Dimethyl ether has high cetane number and low temperature reaction characteristics. These mean that blending small amount of dimethyl ether to the spark-ignited engine would be helpful for improving the performance under lean conditions. Spark timing is one of the important factors influencing the engine combustion. Thus, it is necessary to investigate performance of the dimethyl ether-blended gasoline engine under various spark timings. The engine was run at 1400 rpm, a manifolds absolute pressure of 60 kPa and a constant excess air ratio of 1.20. Test results showed that the addition of dimethyl ether resulted in the raised indicated mean effective pressure for the gasoline engine. Over increased and decreased spark timing tended to cause the dropped indicated mean effective pressure. The coefficient of variation in indicated mean effective pressure was diminished with the spark timing advances and dimethyl ether addition. NOx and HC emissions were dropped with the spark timing decrease. NOx emissions from the dimethyl ether-mixed gasoline engine are decreased with the decrease of spark angle.