Considering the uncertainty of soil parameters and soil strain softening characteristics, the reliability theory is used to establish the limit state equation of the slope progressive destruction, which is to calculate the slope probabilities for the partial failure and the progressive failure. The mode of failure considered here is that failure initiates within an assumed slip surface in the ‘weakest’ segment and progresses outwards from that segment along the slip surface. The reliability analysis method of the slope progressive failure can well reflect the partial slope body failure including its emergence, extension and its influence on the entire slope reliability. Then we can determine the most realistic failure propagation path and provide a theoretical basis of slope stability analysis. The example shows that the partial failure probability of each segment along the slip surface is not equal. Initiating from the eighth segment, the failure passes up at first and then down to the toe, which is different from the traction type failure, initiating from the toe and passing to the top, and the passage type failure, initiating from the top and passing to the toe.