Abstract: The emulsified fuel was prepared through selecting appropriate compound-surfactants on the basis of the HLB (hydrophilic and lipophilic balance) value and the specific emulsification technology. Comparative experiments between the emulsified fuel and diesel fuel were undertook in the model 1135 diesel engine, and the difference in engine economical performances and emissions characteristics between them were studied. The results indicates that the emulsified fuel result in significant decrease in the emissions of soot and NOX and proper increase in fuel-efficiency without modification in the engine structure compared with the diesel fuel; especially for the emulsified diesel with accelerant ferrocene. Besides, various water-content ratios will affect the combustion of the emulsified diesel fuel, and an appropriate one for this engine is 13% in volume after considering fuel-saving and emissions.