Abstract: Classical Rankine and Coulomb earth pressure theories are both calculated on the basis of limit equilibrium state. Thus they are not appropriate for foundation pit engineering because the displacements must be strictly controlled. Cohesive soil slope supported by flexible retaining structure is studied. It considers the influence of the soil arching effects, the value of the internal friction angle and cohesive force between flexible retaining structure and soil, and the value of the internal friction angle and cohesive force between soil and soil. The potential slope sliding surface is searched. The formulas of the passive earth pressure of cohesive soil under nonlimit state against flexible retaining structure is derived via Mohr circle of stress, micro layer analysis method and static equilibrium. The difference between the theory in this paper and Rankine theory is researched from analysis of engineering example. The passive earth pressure calculated by the theory in this paper is smaller. The location impacted by resultant force of the passive earth pressure is lower. The distance from the location to the bottom of the pile is 1.5 percent smaller than that of Rankine theory. The potential sliding surface is a curved surface of horizontal angles decrease with depth. The scope of potential sliding surface is less than the scope of sliding surface under Rankine limit state.