In response to the requirements for high-precision measurement of form and position errors, a form and position error measurement system has been built using position sensitive detectors (PSD), which have the advantages of high accuracy, high sensitivity, fast response, and easy integration with other systems.The system uses laser beams as reference lines and 2D position sensitive detectors as photoelectric conversion devices, Through mobile terminal software, real-time display of the position changes of sampling points relative to the reference line can be achieved, and the shape and position error evaluation results can be quickly output using the least squares method, which is faster and more stable compared to traditional measurement methods.The system measures the straightness of the linear guide rail and evaluates the uncertainty based on single point measurement and measurement system angle.The experiment shows that the standard uncertainty based on single point measurement is 5.9μm, and the standard uncertainty based on measurement system is 7.4μm.This verifies that the system has reliable measurement results.