Abstract:Three equal gauge blocks are commonly used length standards in calibration laboratories. Their deviation values are widely used in length measurement and calibration. The accuracy of their measurement values is directly related to the traceability of measurement values and the accuracy of calibration results. The contact interferometer is used to measure the center length of the three equal steel gauge blocks, establish the measurement model, evaluate the uncertainty of the measurement results, give the standard uncertainty, degree of freedom, sensitivity coefficient and uncertainty components of the main input variables that affect the measurement results, calculate the composite standard uncertainty, and finally give the expanded uncertainty of the measurement results of the three equal steel gauge blocks. And discuss, analyze, control and reduce the feasibility of uncertainty components.