Optical　properties　and　surface　structures　of　InAs/GaAs　self-assembled　quantum　dots　(QDs)　grown　on　2　nm　In0.2Ga0.8As　and　x　ML　GaAs　combined　strain-buffer　layer　were　investigated　systematically　by　photoluminescence　(PL)　and　atomic　force　microscopy　(AFM).　The　QD　density　increased　from　∼1.7×109cm-2　to　∼3.8×109cm-2　due　to　the　decreasing　of　the　lattice　mismatch.　The　combined　layer　was　of　benefit　to　increasing　In　incorporated　into　dots　and　the　average　height-to-width　ratios,　which　resulted　in　the　red-shift　of　the　emission　peaks.　For　the　sample　of　x=10　ML,　the　ground　state　transition　is　shifted　to　1350　nm　at　room　temperature.