Abstract: Double mental cyanide (DMC) is a catalyst for the ring-opening copolymerization of carbon dioxide and propylene oxide. DMC catalysts are organometallic complexes with crystal structure, and their catalytic activity is closely related to crystallinity. The addition of ligand and co-ligand can destroy the cubic crystal structure, increase the amorphous structure and reduce the crystallinity. A number of studies have proved that tert-butanol as the ligand DMC catalyst has high activity, but there are few reports on the use of co-ligand. In this paper, DMC catalyst was modified with different co-complexing agents (Span80, Tween80, D400, D2000), which decrease crystallinity, catalyst particle size and eventually increase catalyst activity. The properties of the catalyst were investigated by copolymerization of PO with CO₂. The results showed that the catalytic activity of DMC+D2000 modified with D2000 as co-ligand was 1547 g/g_cat. The molar fraction of carbonate unit in the polymerization product was 25.3%, and the selectivity was 92.1%.