Rankine’s theory is limited to solving the earth pressure where the wall back is vertical and smooth and the displacement of the fill behind the wall reaches the limit state. It is of great significance to carry out theoretical research for non-limit active earth pressure on inclined rough wall backs. The viscous fill slipper behind the wall is divided into two parts, the elastic region and the plastic region. Based on the principle of virtual work in the non-limit state, an energy conservation equation is established, and the formulas for tension crack depth and potential slip surface are derived. On this basis, the expressions for horizontal stress and vertical stress are obtained through the Mohr stress circle in consideration of the soil arch effect. Moreover, the theoretical expressions for the non-limiting active earth pressure distribution,the magnitude of the resultant force,and the position of the resultant force’s action point are derived by establishing the force balance equation using the horizontal layer analysis method. When the Rankine’s hypothesis is met, the Rankine’s crack depth, slip surface inclination, and resultant force values are special solutions. The validity of the formulas is verified by two model tests. The research manifests that the tensile crack depth is positively correlated with the internal friction angle φ_m of the fill, the cohesion c_m of the fill, the wall-soil friction angle δ_m, the wall-soil cohesion c_wm, and the wall displacement ratio η, while negatively correlated with wall back inclination ε. The inclination angle of the potential slip surface has nothing to do with c_m, but increases with the growth of ε, φ_m, and η, while the influence of δ_m and c_m is opposite. When the wall back is smooth, the earth pressure is approximately linearly distributed, and the position of the resultant force is close to that obtained from the Rankine’s solution; when the wall back is rough, the earth pressure distributes in a convex curve, with the upper part larger than the Rankine’s solution, and the lower part smaller than the Rankine’s solution. Earth pressure declines with the increase of η, φ_m, and c_m, and its peak value increases with the shrinkage of ε, but is rarely affected by c_wm. The position of the resultant force acting point can only be lower than the Rankine’s solution in the presence of large displacement of the inclined retaining wall.