As a novel collector, O-isopropyl-N,N-diethyl thionocarbamate (IPDTC) was designed and synthesized for copper-sulfur flotation separation. Density functional theory calculations were performed to investigate the electronic structures of IPDTC. The results showed that IPDTC had higher energy of the highest occupied molecular orbital but lower electronegativity than O-isopropyl-N-ethyl thionocarbamate (Z-200). It was predicted that IPDTC had strong collection ability according to the reaction energy criteria. Flotation results demonstrated that the collecting ability of IPDTC to chalcopyrite and pyrite was stronger than that of Z-200. Then, the flotation mechanism was analyzed by measurements of surface tension, adsorption capacity, XPS, FTIR and zeta potential. These results indicated that IPDTC could reduce the solution surface tension. The adsorption capacity of IPDTC on chalcopyrite was higher than that on pyrite, consistent with the results of the flotation tests. FTIR, zeta potential and XPS results also demonstrated that IPDTC was strongly absorbed on the chalcopyrite surface by formation of Cu—S—C bonds, but showed a weak affinity on the pyrite surface.