Based on the occurrence characteristics and mining technological conditions of deep zone of the No.100 orebody in Gaofeng Mining Ltd., a modified mining method is proposed, that is, the Pre-Roof-Controlled Mechanized Sublevel Mining with Backfill. According to the method, blocks are divided along the strike of the orebody, and in a block, 10m high sublevels are fragmented through upward medium-length hole blasting. Undercutting is performed for each sublevel, and mined-out space is supported through grouting or bolts. The modified mining method offers high mining efficiency and excellent stoping safety performance, simplifies filling procedures and cuts operational cost.