Space gravitational wave detection is highly sensitive to low-frequency gravitational radiation within the range of 0.1 mHz to 1 Hz. This frequency band is rich in astronomical events and high-intensity gravitational wave sources, making it a crucial area of research at the forefront of fundamental science. A space-based detector consists of three identical spacecraft flying in an equilateral triangle formation, essentially a giant Michelson interferometer placed in space. The space-time metric is altered when gravitational waves pass through. This "ripples in spacetime" can be reconstructed by observing variations in the distance between two freely suspended test masses. However, the point-ahead angle, which arises during the transmission of laser light over distances ranging from tens to millions of kilometers between two satellites in the gravitational wave constellation, varies due to residual seasonal variations and orbital evolution, making it challenging to fully optimize through orbital parameters alone. The Point Ahead Angle Mechanism (PAAM) is used to correct the beam offset and the residual point-ahead angle errors. It is a prerequisite for establishing inter-satellite laser links and ensuring that the space-based gravitational wave detection laser interferometry system enters the stage of scientific measurement. Additionally, since the disturbances acting on the test masses are extremely minimal, any change in the path length measured by the interferometer arms is attributed to gravitational waves. Thus, the PAAM is required to overcome parasitic displacement to the pico-meter level and ensure very rigid rotation perpendicular to the beam propagation direction to achieve nano-radian accuracy.It is an unprecedented challenge to evaluate the essential performance of the PAAM in terms of both precise pointing accuracy and displacement measurements. The RIJNEVEL N research team developed a picometer-stable scanning PAAM for the LISA mission and tested its performance using a triangular resonant cavity. Specifically, the mechanism was in a closed-loop state at three different positions in a vacuum tank of 10^-4 mbar and a temperature environment of $\mathrm{14}\mathrm{\mu }\mathrm{K}/\mathrm{H}{\mathrm{z}}^{\mathrm{1}/\mathrm{2}}$. The experimental results proved that the angle jitter noise amounted to below 8 nrad/Hz^1/2 (0.1 mHz~1 Hz) and the parasitic displacement noise was within 1.4 pm/Hz^1/2 (0.1 mHz~1 Hz), meeting LISA's requirements. However, only displacement noise can be directly measured using the method based on a triangular resonant cavity. Angle noise is indirectly decoupled from angle jitter and path length. Consequently, the accuracy of angle measurement is affected by length measurement noise. Differential Power Sensing (DPS) technology detects the optical axis misalignments along horizontal and vertical direction by received optical power in four quadrants. This technique for measuring variations in laser angles is quick and accurate. Nevertheless, the precision and noise level of incoherent measurements are restricted to microradians, which is inadequate for determining the relative laser angles in space gravitational wave detection applications. Another promising precision angle measurement technology for space applications is Differential Wavefront Sensing (DWS) technology, which is a phase angle sensitive approach with a sensitivity of three to four orders of magnitude using a Quadrant Photodiode (QPD) as the detector. It can integrate angle and displacement measurement in a compact optical path by designing a reasonable laser interference system. Angle values are solved by differential phase of the QPD, while displacement values are computed using the average phase. The correlation problem between displacement and angle noise is essentially resolved by DWS technology, effectively enhancing system stability and dependability compared to the triangle resonant cavity method. DWS technology outperforms DPS technology in terms of measurement accuracy. In 2023, researchers such as ZHU Weizhou from Institute of Technical Physics and GAO Ruihong from Institute of Mechanics, Chinese Academy of Sciences, utilized DWS technology to evaluate the performance of a developed PAAM. The result showed that the optical path delay noise introduced by the mechanism's deflection was less than 10 pm/Hz^1/2 (1 Hz~10 Hz). However, there is still significant measurement noise in the low-frequency band below 1Hz, which requires further exploration.This paper presents a heterodyne interferometric optical system designed on the foundation of Gaussian beam interference theory, incorporating DWS technology to achieve high-precision, integrated measurements of both angle and distance. In contrast to the displacement decoupling method utilized in triangular resonant cavity systems, the DWS approach to angle measurement has demonstrated enhanced reliability. The PAAM is placed on the measurement optical path of the heterodyne interference system, establishing a self-closing loop for one-dimensional deflection using angle values from piezoelectric ceramics and capacitive sensors. The angle noise and displacement noise were independently decoupled with the readout phases of the measuring and reference interferometers. The experimental results show that the pointing control noise was better than 10 nrad/Hz^1/2 (10 mHz~1 Hz), and the parasitic displacement noise stayed within 10 pm/Hz^1/2 (20 mHz~1 Hz) after the system was placed in a vacuum chamber for 72 hours and reached a thermal equilibrium with a temperature of 0.67 mK/Hz^1/2 (10 mHz~1 Hz). This mechanism exhibited lower pointing control noise and parasitic displacement noise in the low-frequency range, compared to the test results of domestically advanced PAAM. This validates the PAAM performance indicators and offers a reference for advancing space gravitational wave detection. However, it still lags behind international PAAM and needs further optimization. Meanwhile, according to the noise analysis results of the testing system, it is necessary to focus on overcoming the temperature drift effect and using high-precision positioning stage to further reduce the alignment deviation of the optical path in subsequent testing, thereby suppressing the tilt length coupling noise caused by lateral offset. Overall, this work contributes to enhancing the system resolution of pointing and displacement measurement and is widely applicable to optical precision measurement systems based on laser interference.