Abstract: To resolve the problem of using only lime as depressor at Cu-S separation in a copper mine ore-dressing plant in Jiangxi, and bringing environment pollution when pulp pH above 12, causing scale on equipment and pipe, then using a new depressor DT-4^# which was researched by Jiangxi University of Science and Technology instead of mostly lime. For the ore to carry on Cu-S bulk flotation and then regrinding and Cu-S separation flotation test, realized the effective Cu-S separation in low-basicity pulp（pH=8）and obtained copper concentrate with a copper grade 23.45% and recovery 90.38%, and sulfur concentrate with a sulfur grade 44.67%  and recovery 91.63%.

Key words: Copper ore, Cu-S bulk flotation, Cu-S separation under low-basicity, New depressor DT-4^#