Abstract: The thin layer element method is used to study the active earth pressure under non-limit state. It is considered that the earth pressure against the back of a retaining wall is due to the thrust exerted by a sliding wedge of the soil between the back of the wall and a plane which passes through the bottom edge of the wall. The basic equations are proposed by considering the equilibrium of the forces and moments on a thin-layer element of the wedge. By using the equilibrium equations, the coefficients of earth pressure, the unit earth pressure, the resultant force of earth pressure and the acting point of the resultant force are obtained. The effects of the internal frictional angle of backfill, the frictional angle between the wall and the backfill and the displacement ratio of the wall on the lateral coefficient of earth pressure, the earth pressure, the resultant force of earth pressure, the acting point of the resultant force are investigated. The discussions indicate that if they are designed according to the limit equilibrium theory, it will be dangerous for the overturning stability of retaining walls with the active translational movement mode under non-limit state. Moreover, the distributions of the active earth pressure computed by the deduced formula agree with the measured data of the engineering case well.