In order to solve higher air velocity in -470 south tunnel and problem of sharing return airway between No. 4 and No. 6 mining area, south limb ventilation system optimization technique of -470 mining level has been proposed. The return airway of the No. 4 mining area is changed from return airway to intake airflow roadway with separating its system of No. 4 and No. 6 mining area. With optimization technique of air velocity in -470 south tunnel reduced from 7.44m/s to 6.3m/s and complete separation of return airway system between No. 4 and No. 6 mining area, the ventilation resistance of southern ventilation shaft has decreased from 3 300 Pa to 2 530 Pa and electricity consumption from 748 800 kwh to 475 200 kwh, which saves 2.38 million yuan electricity charge per year.