Due to strict control for the displacement of retaining structure in excavation engineering, the theory of soil pressure in non-limit state should be considered in the calculation of soil pressure of limited soils. However, most previous studies were confined to the earth pressure of sandy limited soil under non-limit state, and the calculation methods are based on traditional Rankine’s earth pressure theory which is not applicable in semi-infinite boundary condition. In view of this, for cohesive limited soils which do not meet the semi-infinite boundary conditions, we divided the trapezoidal sliding wedge soil into blocks, and established the differential equation of earth pressure strength of cohesive limited soil at non-limit state according to the curves of mobilized angles of internal friction and external friction and mobilized cohesion vs. displacement angle, respectively. Furthermore, we derived the calculating formula for earth pressure of cohesive limited soils at non-limit state. Calculated values are larger than measured values in the range from soil surface to a certain depth of the pit; while beyond that depth, the calculated values conformed well with measured values but differed greatly from Rankine’s value. In general, the calculation method presented in this paper is reasonable and feasible.