Equivalent　sand-grain　roughness　was　carried　out　with　CFD　method　to　investigate　the　effects　of　dust　and　insects　on　the　performance　of　a　1.5MW　horizontal　axial　wind　turbine.　The　results　indicate　that　surface　roughness　especially　on　the　leading　edge　seriously　decreases　the　aerodynamic　performances　of　the　airfoils　and　the　roughness　sensitivity　increases　with　an　increase　in　the　angle　of　attack　(AOA).　The　roughness　sensitivity　of　the　leading　edge　increases　with　the　increase　in　AOA　as　well,　and　the　roughness　located　on　the　trailing　edge　of　the　pressure　side　could　improve　the　aerodynamic　performance　to　some　extent;　The　roughness　located　on　the　3D　blade,　especially　near　the　tip,　seriously　decreases　the　aerodynamic　performance;　The　total　effect　of　the　surface　roughness　on　the　blade　is　not　a　linear　superposition　of　local　effects　of　the　surface　roughness　along　the　span　of　the　blade,　but　a　result　of　comprehensive　effects.　This　research　can　provide　a　valuable　reference　for　the　mechanism　of　the　effect　of　surface　roughness　and　aerodynamic　optimization.　©2014　Chinese　Society　for　Electrical　Engineering.