Abstract: Based on an analysis of the bottom failure mechanism during foundation pit excavation in the soil layer with high artesian water pressure, a method for calculating the critical thickness of the bottom plate is suggested by use of the yield-line method in plastic limit analysis. This method is able to consider influences of the pit dimension, the strength behavior and the failure mechanism of the bottom soil layer on the bottom heave stability. The suggested method and the traditional method are used for analyzing the bottom plate stability of seven foundation pits. The analytic results are compared, and it is shown that the present method is more realistic for evaluating the bottom heave stability than the traditional method.