The　effects　of　phosphate　coating,　electroless　Ni-P　coating　heat　treated　at　400°C　and　electrodeposited　Fe-Ni-P　alloy　coating　on　fatigue　property　have　been　examined　by　three-point　cyclic　bending　test.　The　damage　process　of　the　surface-treating　coatings　has　been　investigated　by　system　analysis　method.　The　results　reveal　that　the　fatigue　damage　of　the　phosphate　coating　is　a　continual　process　and　the　fatigue　damage　of　electroless　Ni-P　coating　and　electrodeposited　Fe-Ni-P　alloy　coating　are　a　short　process.　The　results　also　show　that　the　crack　of　coatings　initiates　when　the　slip　bands　occur　on　the　surface　of　base　steel,　and　the　system　analysis　method　is　effective　in　the　surface　fatigue　damage　detecting.