Abstract: In the traceability of length standards of different sizes, in order to solve the problems of lack of effective error analysis and low measurement efficiency of mirror reflection laser tracking interferometric length measurement, the length measurement error caused by the plane mirror adjustment resolution and flatness was studied. The allowable range of plane mirror angle adjustment for different lengths was obtained. The model of mirror reflection laser tracking interferometry was established, and the source of measurement uncertainty of the model was analyzed. The influence of plane mirror angle adjustment was simulated. The length measurement comparison experiment of coordinate measuring machine and the plane mirror angle adjustment experiment were carried out. The experiment shows that the E_n verification result of length measurement comparison is less than 1, which proves the accuracy of length measurement uncertainty. Through the plane mirror angle adjustment experiment for different lengths, the measurement results with measurement uncertainty of 3 \textμm (length 1 m) and 3.7 \textμm (length 2.5 m) were obtained. The measurement efficiency was improved by 56%. Experiments verify the accuracy and efficiency of this method. This method realizes the high-precision measurement of length and the analysis of measurement uncertainty.