Fuel oil 180# was emulsified by the mixed emulsifier of Tween80 and Span80. Effects of the HLB value and dosage of the mixed emulsifier on the stability, viscosity and dispersed particle size of the emulsions were investigated, and effects of the mixed emulsifier and the amount of added water on the residual carbon and the heat value of the emulsions were also investigated. The experimental results showed that the stability and the viscosity of the water-in- fuel oil emulsions decreased as the HLB value of the mixed emulsifier increased from 6 to 10, however, their dispersed particle size increased; and the stability and the viscosity of the water-in-fuel oil emulsions increased as the mixed emulsifier dosage increased, however, their dispersed particle size decreased. The heat value and the residual carbon of the emulsions decreased as the amount of added water increased, while the mixed emulsifier dosage unchanged. Compared with fuel oil 180#, the heat value of the oil with the per unit mass in the emulsions increased.