Abstract: The mutual solubility and the physicochemical properties of the ethanol-diesel-biodiesel blend fuel were investigated, and the power and fuel economy and emission characteristics of the diesel engine were measured under the condition of burning diesel fuel and the ethanol-diesel-biodiesel blend fuel. The results show that ethanol and diesel fuel and biodiesel can steadily mutually solubilize when the temperature is higher than 10℃ and the volume fraction of biodiesel is more than 17.6%. As the mixed proportion of alcohol gets larger, the combustion and emission circumstances of diesel engine burning the ethanol-diesel-biodiesel blend fuel are that the brake specific fuel consumption increases gradually, that the brake specific energy consumption does not change so evidently though, that the torque increases gradually, that the smoke decreases significantly, that the CO emission decreases significantly at the medium and high loads, that the HC emission increases obviously, that the NOx emission does not basically change, and that the peak value of the maximum combustion pressure and the rate of heat release increase gradually as well as moving back.