In　this　paper,　the　fatigue　crack　growth　rate　of　15CrMo　steel,　a　typical　gas　cylinder　material,　is　studied　under　the　condition　of　simulating　the　actual　working　condition　of　gas　cylinder.　The　low-frequency　corrosion　fatigue　tests　with　stress　ratio　of　0.1　and　0.5　are　carried　out　in　air　and　different　concentrations　of　wet　hydrogen　sulfide　environment.　The　relationships　between　da/dN　and　Delta　K　are　expressed　by　Paris　equation.　The　results　show　that　the　crack　growth　rate　in　hydrogen　sulfide　environment　with　concentration　of　200　ppm　is　27　times　higher　that　in　air.　The　addition　of　corrosion　environment　greatly　fasts　the　crack　growth　rate　of　15CrMo　steel.　With　the　increase　of　H2S　concentration,　the　crack　growth　rate　increases　exponentially.　With　the　increase　of　stress　ratio,　the　average　stress　increases,　the　crack　closure　effect　decreases,　the　crack　tip　is　fully　opened,　and　the　contact　area　with　corrosion　medium　increases,　which　results　in　the　increase　of　crack　growth　rate.