To the inclined rectangle plate subjected to forces acting longitudinally and laterally, the analytical solution of deflection, stress and inner force, considering the influence of inner force in central surface on the bending of the plate, were given by using the theory of plate and energy method. In accordance with the characteristics of structural form of rock layers in horizontal section top coal sublevel caving for the mining steep seam, deflected deformation rules of the roof and evolution path along influencing factors were discussed, the critical technical parameter of horizontal section top coal sublevel caving was got, and engineering technique measures to control strata movement were given. It is shown that, the deflected deformation and inner force are related to plate material, geometrical properties and inclined angle of the plate with obvious nonlinear properties. Then the reasonable range of horizontal section altitude of top coal sublevel caving is between 20m and 30m. The severest area of strata movement is in the central of mined-out area along mining, the upper part of subsidence area must be filled to reduce the length of hanging roof and retard the movement of overlying strata, further control the ground subsidence.