Abstract: In theory,there is a rigorous deducing process for the Laslett algorithm and the generalized H-H algorithm under the mean trace length estimation of discontinuities.However,they have different accuracies of estimated values on different trace length levels.This study carries out tests on the accuracy of estimated values from both algorithms and evaluates their applicability, based on the full-trace length data of excavated slopes.Because the height of test windows in engineering are small,this paper has amended the estimated values of the generalized H-H algorithm.The values are calculated under the conditions of small test window and long trace length level.The research results indicate that(1)under the conditions of small test window and short trace length level, the Laslett algorithm is adopted; (2)under the conditions of small test window and long trace length level,the generalized H-H algorithm is adopted. A modified coefficient 2 is suggested.