Redox initiator of ammonium persulfate/sodium bisulfite, styrene,butyl methacrylate, acrylamide and methacryloyloxyethyl trimethyl ammonium chloride as the synthesis of the monomers , which synthesizing tetrapolymers heavy demulsifier styrene / butyl methacrylate / acrylamide / methacryloyloxyethyl trimethyl ammonium chloride by emulsion copolymerization . The structure of tetrapolymers heavy demulsifier was characterized by Infrared Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. The optimum conditions of synthetic quaternary copolymer heavy demulsifier were as follows: reaction temperature 65 ℃, emulsifier dosage 1.6% (the total mass quality system) , initiator dosage 1.1% (the total mass of the monomers) , monomer concentration 30% . Using Shengli Oilfield chenzhuang heavy oil simulated heavy oil emulsion to evaluate the performance of homemade tetrapolymers heavy demulsifier.Effects of demulsification conditions on demulsification performance. Under the condition of demulsification temperature 60 ℃, demulsification dosage 200 mg/L , demulsification time 120 min, the dehydration was reached up 89.3% , the oil content of water 198.6 mg/L, the oil-water interface was neat and clear water prolapse. The performances tests of the O/W demulsifier were superior to those of industrial demulsifiers AE-8051, YT-100, SP-169, BQ-05.