In　this　paper,　the　fatigue　crack　growth　rates　of　typical　pressure　vessel　material　4130X　under　different　corrosion　conditions　are　investigated,　and　the　effects　of　corrosion　modes　and　loading　frequency　on　the　fatigue　crack　growth　rate　of　4130X　are　discussed.　The　results　show　that　under　the　same　loading　conditions,　the　pre-corroded　crack　propagation　rate　is　increased　by　1.26　times　compared　with　the　uncorroded　specimens.　The　plastic　deformation　mechanism　of　the　crack　tip　in　air　is　dominated　by　phase　transformation　but　the　hydrogen　introduced　by　pre-corrosion　causes　a　small　number　of　dislocations　at　the　crack　tip.　The　crack　growth　rate　obtained　by　corrosion　fatigue　is　four　times　that　of　the　uncorroded　specimen,　and　the　fracture　surface　shows　a　strong　corrosion　effect.　The　molecular　dynamics　simulation　shows　that　the　hydrogen　atoms　accumulated　at　the　crack　tip　make　the　plastic　deformation　mechanism　dominated　by　dislocation　in　the　crack　propagation　process,　and　the　coupling　interaction　between　low　frequency　and　the　corrosion　environment　aggravates　the　hydrogen　embrittlement　of　the　crack　tip.　In　the　air　condition,　the　loading　frequency　has　no　obvious　effect　on　the　crack　growth　rate:　when　the　frequency　decreases　from　100　Hz　to　0.01　Hz　and　other　conditions　remain　unchanged,　the　fatigue　crack　growth　rate　increases　by　1.5　times.　The　parameter　n　in　the　Paris　expression　is　mainly　influenced　by　frequency.　The　molecular　dynamics　simulation　shows　that　low　frequency　promotes　crack　tip　propagation.