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In order to study the influence of hydrogen environment on the initiation and propagation of fatigue cracks in duplex stainless steel and establish the correlation mechanism between the fatigue strain microstructure evolution and hydrogen induced cracking in hydrogen environment，slow strain rate tensile and fatigue crack growth rate tests were carried out on 2205 duplex stainless steel specimens in 5 MPa hydrogen and 5 MPa nitrogen environments.Results showed that the hydrogen embrittlement sensitivity of 2205 duplex stainless steel was not high in the process of slow strain rate tensile in hydrogen environment，while it was significant during the fatigue process.The fatigue crack growth rate of 2205 duplex stainless steel in a hydrogen environment of 5 MPa was 18 times higher than that in a nitrogen environment.Hydrogen could promote local plastic deformation around the fatigue crack tip of 2205 duplex stainless steel and further led to hydrogen-induced cracking.In the process of fatigue deformation of 2205 duplex stainless steel in a hydrogen environment，different phase structures had different hydrogen-induced cracking mechanisms.The ferrite phase was easy to form a river-like pattern fracture morphology (cleavage fracture)，while the austenite phase fracture appearance mostly presented the characteristics of parallel slip bands.Austenite phase hindered cracks during the cleavage and cracking process of the ferrite phase.