A method for analyzing and evaluating stitching precision based on t distribution statistic was presented aiming at the problem of stitching precision of aspheric surface analyzed by sub-aperture interferometry based on correcting aberration. The residual error was used to implement the regression diagnosis according to the principle of stitching measurement and the feature of stitching model. Then, based on t distribution statistic,the forecast dependent variable in the regression analysis was used to assesse and analyze the stitching precision. The uncertainty in experiment result was analyzed, analyzed result indicates that the expansion uncertainty based on t distribution statistic is 0.362 3λ(0.229 μm), and the expansion uncertainty by the conventional precision evaluating method is 0.234 μm. The results of the two precison evaluating methods are idential basically,which shows the new precison evaluating algrithom overcomes the uncertainty of comparative analyzing method on the premise of ensuring the precision,and also solves the problem that the confident coefficient according to normal distribulion can not reflect the effect of sample root-mean-square reliability on the fiducial probability.