In order to reduce the viscosity of heavy oil in Chennan station of Shengli oilfied，seven kinds of surfactants whose HLB value between 8 and 18 were selected. By measuring the dehydration rate and viscosity reduction rate of the emulsion with single and compound emulsifiers，the emulsifiers which had both good static stability and viscosity reduction effect were selected. The effect of the mass ratio of oil to water，emulsifier concentration，emulsifying temperature and strength on the viscosity was investigated. The results showed that when the emulsifying temperature was 50℃ and emulsifying strength was 2000 r/min×10 min，two kinds of optimum compound emulsifiers were selected，including 25.8% Span80 and 74.2% sodium dodecyl benzene sulfonate，10.1% Span80 and 89.9% sodium dodecyl benzene sulfonate，whose dehydration rate was 21.8% and 23.0% and the viscosity reduction rate was 99.92% and 99.89% at 100 s^-1 respectively when they were put into heavy oil and placed for 5 hrs. The dehydration rate of emulsion increased，the viscosity decreased and the stability deteriorated with decreasing mass ratio of oil to water. The viscosity of emulsion decreased first and then increased with increasing emulsifier concentration. The viscosity of emulsion increased with decreasing emulsifying temperature and increasing emulsifying strength. The viscosity of heavy oil in Chennan station could be reduced from 1964 mPa·s to 35 mPa·s under the emulsifying condition of 5∶5 mass ratio of oil to water， 1% dosage of emulsifier，50℃ emulsifying temperature and 1000 r/min×5 min emulsifying strength.