The uncertainty of evaluation results of sampling rates of linear measurement system by using the data number counting method in one standard signal period,the courses of analysis and evaluation of uncertainty of sampling rate are described in this paper.Some error sources of sampling rate evaluation are discussed.Several main methods about decreasing the sampling rate evaluation errors and evaluation uncertainty have been proposed.Through a group of examples of experiment,the analysis and evaluation results of sampling rate and its uncertainty by using the method in this paper are presented.The course and conclusion of analysis and evaluation of sampling rate uncertainty in this paper, can be applied to the uncertainty evaluation of measurement standards of relative specifications, can also be used in the uncertainty evaluation of sampling rate itself.