<p>AM austenitic steel is increasingly adopted in large pressure vessels owing to its inherent advantages. To investigate the differences compared to the traditional pressure vessels austenitic steel, the strain-controlled fatigue tests of selective laser melting 304 austenitic stainless steel (SLM 304 SS) and type 304 austenitic stainless steel (type 304 SS) are conducted under different strain amplitudes at room temperature (RT). The results indicate that the corresponding internal stress components of SLM 304 SS are higher than those of type 304 SS resulting from the influence of initial microstructure on the dislocation short-range obstacles and long-range resistances, leading to the higher cyclic stress curves of SLM 304 SS. Both SLM 304 SS and type 304 SS exhibit initial cyclic softening behavior, with increasing fatigue cycles, a stabilized cyclic response is observed in SLM 304 SS once the dislocation density reaches a dynamic equilibrium under cyclic loading. In contrast, type 304 SS exhibits pronounced cyclic hardening behavior due to strain-induced martensitic transformation and interactions among deformation twins. Furthermore, a cyclic constitutive model is employed to evaluate the cyclic deformation behavior of both materials. Phase transformation enhancement <i>σ</i>_mt is introduced to directly describe the cyclic hardening behavior of type 304 SS.</p>