Abstract: In order to meet the test and calibration requirements of 100m~3km extra-long focal length, a set of long focal length measurement instrument was designed based on Talbot-Moiré fringes. Aiming at the system parameters affecting the measurement uncertainty, different calibration methods were designed respectively. Experiments were carried out to verify the results. The results show that, after calibration, the measurement uncertainty is 6.4%. Measurement results of the long focal length measurement instrument after calibration, and knife-edge instrument meet the measurement uncertainty formula. The maximum comparison result is 0.64, less than 1. Uncertainty evaluation of the long focal length measurement instrument is reasonable. The research validates the feasibility of calibration methods for system parameters of a long focal length measurement instrument.