Abstract: The paper took the mine pressure monitoring of 42103 working face of Buertai Mine in Shendong Mining Area as the research background, and the sources, action and stability of hydraulic support horizontal force at fully mechanized sublevel caving face were analyzed by methods such as field measurement, theoretical analysis et al. The results show that the horizontal force of support includes active horizontal force and passive horizontal force. The active horizontal force of the two-leg support is larger than the four-leg support. The horizontal force of support was closely related to its stability. The positive effect of horizontal force of two-leg top coal caving support to end face was applied to roof management of 42103 working face of Buertai Mine, which got ideal control results.