Abstract: The discrepencies forward and backward in rerunning levels are usually used as statistic in the accuracy estimate of levelling.The existing methods concerned,however,don't involve verifications on correctness of the error models for the discrepencies,even lack strict and feasible formulae for the estimate.In this paper,the MINQUE of variance components is applied to estimating the variances,and some statistical tests and optimal option of the error models are presented based on the principle of regression analysis.The methods of the estimation and analysis are not only analytically strict but also more feasible.Finally,the advantages and effectiveness of the methods are examined.through a testing computation using first-order class Ⅰ levelling of 175 sections and lines.