The "JJG (Light Industry) 59-2000 MIT Folding tester verification procedure" is suitable for the first verification, subsequent verification and in-use inspection of MIT folding testers. The procedure is based on ISO 5626:1978 "Paper - Determination of Folding Tolerance" and covers the structural parameters, technical requirements and calibration methods of the folding tester. The main content includes the measurement performance requirements of the folding tester, Appearance and component functions, noise control and verification items. The standard strictly stipulates the number of folds, error of indication of spring tension, tension fluctuation value, etc., and provides detailed methods of verification. Through this procedure, the measurement accuracy of refractive instruments and their Reliability in use can be ensured.