Abstract: Dozens of demulsifiers were tested for desalting of Shengli Huangdao crude oil on a static test apparatus. By screening the test results,demulsifiers of alkyl phenol aldehyde polyoxyethylene/propylene ether type were selected. Effects of compositions of the demulsi-fiers on their desalting performances and interfacial tension between oil/aqucous phases are discussed,thus optimum composition of the demulsifier is determined.