NiAl　particles　were　plaswa　sprayed　on　polished　and　blasted　AZ31　magnesium　alloy　substrate　at　different　pre-heating　temperatures(25°C,　150°C,　250°C).　The　flattening　behaviour　of　the　sprayed　particles　and　the　bonding　mechanism　of　the　coating　to　substrate　were　investigated.　The　results　indicate　that　the　central　solidification　area　of　droplets　increases　with　the　increase　of　substrate　temperature.　NiAl-particles　plasma　sprayed　locally　melt　the　substrate　and　pitting　deformation　occurs　on　its　surface.　The　metallurgical　bonding　is　dominant,　leading　to　high　adhesion　strength　of　the　coating　to　substrate.