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.