Abstract: Based on project background of the second mining working face of Shenghua Coal Mine, the paper explained mechanism of rib fall of coal wall of the second mining working face of residual coal, analyzed cases of rib fall of coal wall under different support resistances by theoretical calculations and computer numerical simulation, compared effect of the support resistance on the rib fall of coal wall under the condition of residual coal and entity coal, and drew the conclusions as follow: ① The extent of rib fall of coal wall decreased with the increase of support working resistance, and there was a linear relationship between the maximum depth of rib fall of coal wall and supporting strength, and the extent of rib fall of residual coal wall is much larger than the extent of rib fall of entity coal wall under the same working resistance. ② In the condition of entity coal, the extent of rib fall of coal wall is not serious when working resistance reached 8 000 kN. But in the condition of residual coal, the working resistance must reach 9 000 kN, then the roof falling and breakage depth of coal wall can be controlled. At last, the support resistance of the second mining working face of Shenghua Coal Mine was determined as 9 000 kN.