Abstract: A new method to locate critical slip surface of soil slop named Wang-Yu algorithm is proposed.This method's theory is intelligible,further more it has strong capacity of global optimum.Wang-Yu algorithm obtains the local optimum by calculating the trial slip surface in large-scale area,then takes the local optimum as initial value to proceed a small-scale and high-precision search in order to locate the critical slip surface finally.Two examples are given and the results are satisfactory.This method proved that it is applicable for complex soil slope.