Motion precision of scanning mirror is vital for motion compensation results of imaging spectrometer. So a set of scanning mirror testing equipment was developped to test scanning mirror′s motion precision. Firstly, the motion compensation principle was analyzed and the theory motion compensation curve was given. Then according to 15 m GSD and 2% degradation of system MTF, the scanning mirror′s position and speed precision target was confirmed. At the same time the relationship between motion compensation times and relative rotation error was outlined. Based on 1/3 principle, the guide line of scanning mirror′s motion precision testing equipment was proposed. In succession a set of testing equipment found on 0.8″ absolute optoelectronic encoder was established. The testing precision of testing equipment was analyzed carefully from the testing method error and the encoder′s error aspects. Finally, scanning mirror′s motion precision testing experimentation was carried out by the testing equipment. The testing results indicate that the scanning mirror′s position precision is better than 3″±1.2″, speed precision is 5.6%±1.29% when 4 times compensation and 3.85% ±1.29%when 6 times compensation. These precision results meet the requirements of imaging spectrometer for scanning mirror. Favorable imaging property of the imaging spectrometer proves that the proposed testing method and equipment is suitable for scanning mirror′s check and accept.