The　idle　performance　of　a　gasoline　engine　equipped　with　a　methanol　injection　system　using　different　methanol-gasoline　blends　was　investigated.　The　idle　speed　and　engine　temperature　were　controlled　at　800,r/min　and　90,　,　respectively.　Proportions　of　methanol　was　increased　from　0%　to　100%　gradually　by　adjusting　the　injection　pulse　width　of　methanol　and　gasoline,　and　the　concentration　of　the　air-fuel　mixture　was　controlled　around　the　theoretical　air-fuel　ratio.　With　the　increase　of　proportion　of　methanol　to　gasoline,　experimental　results　show　that　both　combustion　efficiency　and　indicated　thermal　efficiency　are　increased;　combustion　rate　is　increased　and　combustion　duration　is　decreased;　cyclic　variations　coefficient　of　indicated　mean　effective　pressure　is　decreased;　the　amplitude　of　0.5　order　angular　vibration　of　the　crankshaft　free-end　position　reflecting　cylinder　to　cylinder　variations　is　decreased.　Average　values　of　HC,　CO　and　NOx　emissions　are　decreased　remarkably　with　the　increase　of　proportion　of　methanol　to　gasoline.　©,　2014,　Chinese　Society　for　Internal　Combustion　Engines.　All　right　reserved.