In order to solve the problem of the coal wall rib spalling in 72909 fully mechanized mining face, numerical simulation of coal wall water injection stability control were analyzed, combined with the specific geological conditions of 72909 working face, the concrete design of the working face advance water injection scheme was carried out, and the implementation effect was analyzed. The results showed that when the moisture content of coal was 4%~5%, the coal wall was stable. After water injection in the working face, the rib spalling frequency of coal wall was reduced by about 80%.