In order to improve the demulsification effect of the crude oil emulsion from Bohai Sea S oil field，styrene-maleic anhydride copolymer（SMA） was synthesized from styrene and maleic anhydride radical polymerization，the polybranched water-soluble demulsifier TS-Z806 was synthesized by graft copolymerization of SMA and 1.0 G PAMAM，the main chain being of polystyrene-maleic anhydride copolymer，and the side chain being of 1.0 G PAMAM. The demulsification effect of the demulsifier on crude oil emulsion at different temperatures of 50—90 ℃ was investigated，and compared with that of polyether demulsifier JM-01，the demulsifier was used for the first time in Bohai Sea S oil field. The results of laboratory and field tests showed that the demulsification effect of polyether demulsifier JM-01 on crude oil emulsion was worse when the temperature was higher than 70 ℃ However，TS-Z806，a non-polyether demulsifier，still had good demulsification effect on crude oil emulsion at the higher temperature. The demulsifier TS-Z806 had shown excellent demulsification performance in treating the produced fluid containing polymer at the confluence of the crude oil comprehensive pipelines in Bohai Sea S oilfield. The demulsifier could obviously improve the water quality of the demulsified water，and the emulsified layer of the upper oil was lower after demulsification，the emulsified layer after dehydration decreased by about 69% . The demulsifier could realize the high-efficient treatment of the polymer-containing produced liquid，and had a good field application prospect.