In Chimashan Copper Mine, the orebody is mid-thick and the rockmass in the hanging-wall is moderately stable. The shorthole shrinkage mining method was used before, however, this method was difficult to meet the production requirements due to severe ore dilution and ore loss, and low productivity.Therefore, as a technical renovation, the sublevel room-and-pillar mining system was tested in which the rooms were designed to be rhombic in order to minimize the exposure area of hanging wall-rocks and to assure the stope stability. The application of the sublevel room-and-pillar system has substantially raised stope productivity, reduced ore dilution and loss, cut mining cost, and offerred useful experiences for other similar orebodies mining.