The vertical foundation stress and horizontal friction of the higher level wharf is taken as an overload, which is converted into the earth pressure and acting on the lower level wharf. Based on the reliability theory and combining with the project example of Naxigou wharf, we analyze the most disadvantageous condition combination and the worst failure mode of the multi-stage gravity wharf. The results show that the anti-sliding stability has a minimum reliability when water-level is the same as the height of the junior and the greater wharf among various kinds of function combinations, which is the controlling condition.