Based on the alternate distance of combined mining working face, the alternate distance Tmin was 43.6~48.6 m calculated by theoretical analysis and count. Through numerical simulation，alternate distance of combined mining working face was greater than 40 m， the change of roof plate displacement and stress was not obvious, and alternate distance of combined mining working face was less than 40 m， the change of roof plate displacement and stress was obvious，with strong mining pressure. Finally，the reasonable alternate distance was set as 40 m， which had certain guiding significance for production.