This　article　studies　the　effect　of　microstructure　on　the　corrosion　fatigue　crack　growth　behavior　of　low　and　medium　carbon　steels.　45　steel　and　15CrMo　were　selected　and　five　typical　microstructures　were　obtained　by　different　heat　treatment　processes.　The　microstructures　of　45　steel　and　15CrMo　after　annealing　and　normalizing　are　both　ferrite　and　pearlite,　but　the　proportions　of　ferrite　and　pearlite　in　the　four　microstructures　are　different.　The　quenching　and　tempering　microstructure　of　45　steel　is　tempered　fine　pearlite.　Corrosion　fatigue　tests　were　conducted　on　specimens　with　different　microstructures　of　the　two　materials.　Expressions　of　corrosion　fatigue　crack　growth　rate　and　da/dN∼ΔK　fitting　curves　of　different　microstructures　were　obtained.　Comparison　of　da/dN∼ΔK　curves　of　45　steel　shows　that　tempered　fine　pearlite　has　the　best　resistance　to　corrosion　fatigue　crack　growth,　and　the　content　of　pearlite　has　a　great　impact　on　the　corrosion　fatigue　crack　growth　behavior　for　specimens　with　the　microstructure　of　ferrite　and　pearlite.　In　the　low　ΔK　region,　the　corrosion　factor　plays　a　dominant　role　in　fatigue　crack　growth,　and　the　corrosion　resistance　of　pearlite　is　weak,　which　leads　to　a　higher　da/dN　in　the　normalized　state.　In　the　high　ΔK　region,　fatigue　factor　dominants,　since　the　fatigue　resistance　of　pearlite　is　strong,　da/dN　of　the　annealed　state　is　higher.　The　experimental　results　of　15CrMo　showed　the　same　crack　growth　rate　change　regulation　as　that　of　45　steel,　which　further　proves　the　effect　of　pearlite　on　the　corrosion　fatigue　crack　propagation　behavior.　©　2022　Jing　Wang　et　al.