Abstract: Based on the classical earth pressure theory to set the thrust line of soil article, the relationship between the lateral interaction force of soil article can be derived from the torque balance equation, consider the conditions which the lateral force of the first and the end soil article parallel to the top when the soil article is small enough, combined with the boundary conditions for solving the "P_i" and "θ", substituting them into the definition of the safety factor to obtianed the safety factor. The law solving the "θ" starting from setting a reasonable thrust line, eliminating the blindness and complexity of the Spencer method to assumes the "θ",to fix the "θ" of the first and the end soil article, making the results closer to the real solu tion. Examples show that the method is simple in calculation, reliability and has other advantages.