Abstract: The soluble characteristic of dieselethanol blended fuel using cosolvent was investigated and its performance and exhaust emission behaviours in a diesel engine were examined. Four ethanoldiesel fuels named as E0, E5, E10 and E15 were prepared with the content of cosolvent being 1.5% and the contents of ethanol being 0 (20# neat diesel), 5%, 10% and 15% by volume, respectively. It was found that the composition of various hydrocarbons in the diesel fuel exhibits significant influences on the soluble characteristic and the addition of 10% ethanol and 1.5% cosolvent in the diesel can prevent the blend fuel from phase separation perfectly. The engine tests indicated that the brake specific fuel consumption increases gradually while the rated power and the maximum torque decrease with a growth in the ethanol content of blend fuel. As to the regulated exhaust emissions, the brake specific emissions of HC, NOx and PM (BSHC, BSNOx and BSPM) increase with the ethanol content in the blend fuel, but the increments of the BSNOx and BSPM emissions are not so obvious as NOx emission. The BSCO emissions tend to reduce with an increase in the ethanol content. Overall, the ethanoldiesel blend fuel with an ethanol content of 10% exhibited the optimum performance on engine operation and exhaust emission controlling.