To achieve real⁃time, multi⁃degree⁃of⁃freedom measurement and feedback on the position and orientation of a robot's end⁃effector, a planar 3⁃DOF non⁃contact measurement system utilizing sensor fusion of a Position Sensitive Detector (PSD) was developed. The system's design involved studying the measurement principle, signal processing circuitry, ambient light interference mitigation, and a nonlinear calibration algorithm. Initially, a 4⁃PSD measurement system was tailored to the PSD sensor's measurement capabilities and the specific needs of planar 3⁃DOF measurement, establishing a mathematical model for the system. The PSD sensor's signal processing was then explored, achieving single PSD signal processing through an operational amplifier and divider, integrated with an MCU and A/D conversion chip for high⁃frequency signal acquisition on a PC. Preliminary tests of the 4⁃PSD system addressed ambient light interference using laser modulation and digital filtering techniques. Calibration of the 4⁃PSD system⁃comprising origin, angle, length, and second⁃order nonlinear calibration-was conducted using a laser displacement sensor, detailing the calibration steps and post⁃calibration error distribution. The designed system boasts a high measurement frequency of 50 Hz, with calibration experiments indicating an average accuracy of 0.49 mm within a 70 mm×70 mm range, achieving a 90% error reduction post⁃calibration. This system fulfills the majority of requirements for high⁃speed, high⁃precision, non⁃contact real⁃time measurement and feedback of robot end⁃effectors.