A theory of adopting strip-filling mining replacing strip coal pillars was put forward and clarified, and the key effects of filling replacement mining was analyzed. Optimum mining pattern was researched based on the width, strength and filling methods of filling bodies. The research results show that in the process of strip-filling bodies replacing coal pillars the strip-filling bodies work as bridge piers. The supporting strength, size and filling methods are designed reasonably to control the movement range of the key layers and to realize the steady transferring of mine ground pressure and effective control of overlying strata’s movement. The subsidence amount of stope’s key layers is closely related with bridge piers’ modulus of elasticity-E and the width-D so that the optimum piers’ modulus of elasticity-E and its width-D is determined by means of studying the relations between the subsidence amount of key layers with filling cost and the piers’ modulus of elasticity-E and its width-D. The stope’s safety factor is determined by the filling bodies’ width and strength and the optimum strength of filling bodies can be determined by studying the relations between safety factor with filling cost and filling bodies’ strength and width.