The point ahead angle mechanism (PAAM) is a key component of the space gravitational wave detection telescope. It can control the displacement of the telescope precisely by inputting voltage or charge to the piezoelectric actuator. Therefore, the displacement response of the piezoelectric ceramic actuator directly affects the pointing control performance of the PAAM. In this paper, the equivalent capacitance calculation method is proposed to quantitatively analyze the displacement response characteristics of piezoelectric actuators driven by charge, and the accuracy and feasibility of the calculation method are verified by numerical simulation and experimental verification. The results show that when a charge amplifier controlled by 5 V, 0.05 Hz~5 Hz sine wave signal is used to drive a certain type of piezoelectric actuator, the maximum deviation of displacement response between the analysis results and the experimental results is within 1.35%, which provides a possible analysis method and realization way for the high-precision pointing control of the PAAM of the space gravitational wave detection telescope.