In order to correctly select the test method which conforms to the normal distribution model and determine the reasonable statistical value of parameters, based on the least squares parameter estimation method, this paper makes a statistical analysis of the median and standard deviation of the test data of multi-stage method and lifting method commonly used in electrical tests. The results show that the two test methods have good consistency with the corresponding median U50 estimation value, but the difference between two statistical standard deviations is large, reaching 42.6%. Therefore, in the test work, especially for the parameter statistics of large-scale insulation test for obtaining standard deviation, multi-stage method should be preferred, not lifting method. Both methods all can meet the requirements of obtaining 50% discharge voltage.