Abstract: At present, the traditional strength reduction method is still widely used in the stability analysis of large multi-slip slope. The traditional strength reduction method, known as synchronous reduction method, is to synchronously reduce the values of c and Pauline of the whole slope rock and soil mass, without considering the difference in anti-shear effect of c and Pauline values in the process of slope instability. In this paper, the numerical simulation software FLAC3D is used to simulate the slope instability. And then the SSR is programmed to calculate the reduction coefficient of c and ,selecting the same set of safety coefficients and the lower limit value, and making a separate reduction. The reduction coefficient of c and is different, which proves that the attenuation of c and is different in the process of slope failure. Based on this, a new double-fold subtraction method is proposed, which is called the synchrotron and post-asynchronous subtraction. The method is used to analyze multi-sliding surfaces slopes and the simultaneous reduction method is used as the reference for calculating method. The comparisons show that the result of synchronization reduction is larger, and more conservative than synchronous and asynchronous reduction. Numerical simulation results of synchronous and asynchronous reduction are in good agreement with the actual monitoring data.