Abstract: In order to have a further study on the distribution law of critical slip surface of soil slope, and find new method which can fast locate critical slip surface, based on the critical displacement field obtained by strength reduction method, the definition of the critical location was given firstly. Then the distribution of the critical location in the critical displacement field was analyzed in theoretical perspective. Finally, 6 examples were analyzed to explain the rationality of results got by theoretical analysis. As to the 6 examples, different methods were used to search for the critical slip surface, some conclusions were got meanwhile. The study show that the critical slip surface and the horizontal displacement contour of the homogeneous soil slope have good coincidence, the value of the critical location is about 0. 42. The critical slip surface and horizontal displacement contour of the layered soil slope with anisotropy have bad coincidence relatively, as to the two-dimension layered soil slope model, the critical slip surface can be got approximately with the value of critical location and smooth curve.