As　an　alternative　fuel,　dimethyl　ether　(DME)　improves　the　combustion　and　reduces　emissions　of　gasoline　engines.　Moreover,　the　control　of　injection　strategies　of　direct　injection　(DI)　gasoline　engines　could　form　the　preferable　stratified　charge,　enhancing　the　performance　characteristics,　especially　under　lean　burning　conditions.　Thus,　the　co-effects　of　injection　strategies　and　DME　addition　on　the　performance　of　a　DI　gasoline　engine　were　investigated　under　the　lean-burn　condition.　Results　showed　that　the　appropriate　injection　ratio　(IR)　during　the　two-stage　injection　strategy　could　exhibit　a　higher　brake　thermal　efficiency　(BTE),　a　lower　cyclic　variation　and　HC　emissions　compared　to　the　single　injection　mode.　Moreover,　the　cyclic　variation　was　decreased　firstly　then　increased,　the　BTE　and　heat　release　rate　were　raised　firstly　then　reduced　with　the　increase　of　IR.　Furthermore,　NOx　emissions　were　increased　firstly　and　then　decreased,　HC　emissions　were　decreased　firstly　and　then　increased　and　the　trend　of　CO　emission　was　increased　constantly.　In　addition,　the　DI　gasoline　engine　blended　with　DME　raised　BTE,　shortened　the　combustion　phase,　eased　cyclic　variation,　increased　CO　emission　and　dropped　HC　emissions　under　tested　conditions.　The　use　of　DME　with　optimum　IR　could　be　a　practical　way　to　improve　the　trade-off　between　BTE　and　NOx　emissions.