Abstract: Taking a mine’s lane filling mining as engineering background, theoretical calculation and numerical simulation are used to analyze the reasonable strength of filling body. The results showed that: theoretical calculations showed that the reasonable strength of filling body is 6.67 MPa; numerical simulation obtained that the reasonable strength of filling body is 0.6 to 0.8 times of the coal’s strength, and numerical simulation is based on the results of vertical stress of isolation pillar and roof subsidence above filling body, the two results are similar, so we can design that the filling body’s strength is 6 MPa to 8 MPa.