Abstract: In this paper, the combustion performance of diesel engine fueled with different proportion of DME-diesel mixture was researched.The result shows that the pressure and the temperature of the cylinder decline sharply and the combustion becomes moderate while the engine is fueled with the admixture of DME and diesel.The ignition delay period is reduced.And the emission performance is significantly improved with the increase in the proportion of DME content in the fuel, for example, NO_x and soot emission decrease.