The classical earth pressure theory only calculates the ultimate earth pressure in translational mode of the retaining wall. In order to get closer to the real engineering situation, it is necessary to develop the theory of non-ultimate earth pressure of the cohesive fill behind the wall under arbitrary load action and arbitrary displacement mode. The concept of equivalent uniform load was adopted to convert any type of load acting on the earth filling surface into uniform load. Based on the classical earth pressure theory, the rigid retaining wall was regarded as a combination of an ideal rigid plastic body and a series of springs, and the soil stiffness coefficient of the clay was obtained, which improved the Coulomb earth pressure theory and derives the general calculation method of the non-ultimate passive earth pressure of the soil in any displacement mode that can consider the arbitrary load. The research results indicate that the distribution and magnitude of passive soil pressure, the position of the resultant force point are closely related to the displacement mode of the retaining wall, the magnitude of cohesive force, and the load acting on the fill surface. When the equivalent uniform load and cohesive force are both 0, this method degenerates into Coulomb soil pressure theory. The model validation results show that the theoretical calculated values are in good agreement with the experimental measured values, proving that this calculation method has certain theoretical significance for calculating the passive soil pressure of cohesive soil under non limit states, and also has practical value for engineering practice.