Flux　surface　preparation　on　ZL101　substrate　was　carried　out　to　form　Ni5Al　coating　by　plasma　spray.　The　mechanism　of　the　coating　was　analyzed　by　calculation　for　interfacial　temperature.　The　effect　of　process　parameters　on　bonding　strength　of　the　coating　was　studied　by　three-factor,　three-level　orthogonal　experiments.　The　results　show　that　preplacing　flux　prior　to　spraying　can　substantially　improve　the　adhesion　of　the　coating,　and　the　temperature　of　sprayed　particles　and　the　substrate　temperature　play　determinative　roles　in　the　interfacial　bonding.　The　optimal　process　parameters　are　the　spray　distance　of　120　mm,　the　specific　quantity　of　prelaid　flux　of　80　mg/cm2　and　the　preheating　temperature　of　573　K.