土坡的稳定分析一直是沿着条分法的思路发展的。由于对土体应力状态条件的忽视和条分法本身的缺陷，使得条分法得到的安全系数在工程中的应用面临激烈的挑战。土体不同条件下的应力状态表现为K₀效应和变化，它对坡体的安全度影响不可忽视。笔者以考虑土体应力状态为条件，应用土的库伦强度定律和摩尔-库伦准则，推导出平面土坡的安全系数计算公式，与条分法的安全系数对比结果说明这种方法具有概念明确、计算简便、定性可靠的重要特点，可以直接提供于工程应用和参考。

The methods for analysis of stability of slope are usually considered, developed and improved along the line of finite slice method. But the safety factor of stability is facing challenge in engineering application. Because of the state of original stress in soil is ignored and disfigurement of finite slice method is in existence at all time. In different conditions of soil consolidation, K₀, the lateral stress coefficient of soil state, has influenced the property of soil and excavation of slope. In this paper, in consideration of the state of soil original stress, the calculating formula for safety factor have been given with applying Coulomb's equation for shear strength of soil and Mohr - Coulomb rule. There are many examples of safety factor using the formula of this paper, which have been calculated and compared with finite slice methods selected from reference literatures. The formula have showed their clear concept, simple calculation and dependable result. They can be used in engineering.