The Cu-S separation tests have been conducted at pH=7~8 with five combined depressants, namely, Starch + pyrogallic acid, sodium hypochlorite + pyrogallic acid, pyrogallic acid + Tannic, sodium hypochlorite + Tannic and calcium hypochlorite + DT-2#. The tests show that calcium hypochlorite + DT-2# is the best depressor for pyrite, which leads to the Cu-S separation at a low alkalinity of pH=7~8 without lime. From the chemical analysis and Raman spectroscopy of the mineral surface, the inhibition mechanism of pyrite at a pH of 7~8 is as following: calcium hypochlorite + DT-2# oxidizes the pyrite surface to produce a hydrophilous film of Fe(OH)3 and CaCO3, which enhances the hydrophilicity of the pyrite surface, and pyrite is fully depressed during the Cu-S separation, thus the separation of copper from sulfur has come true.