Abstract: In order to study the constitutive relation of stainless steel under cyclic loading, austenitic stainless steel S30408 and duplex stainless steel S220503 coupons were tested under monotonic and large-strain ultra-low cyclic loading. Three types of constitutive models were used to fit the stress-strain relationship under monotonic loading, and pertinent constitutive relation parameters were obtained. The cyclic skeleton curves were fitted by the Ramberg-Osgood model, and the parameters of the cyclic hardening were calculated. Furthermore, the parameters of the cyclic constitutive model were calibrated and the test curves were simulated by ABAQUS finite element analysis software. The results show that the G-R-O constitutive model can fit the constitutive relation better under monotonic loading. Under cyclic loading, with the increase of cyclic loops and change in strain amplitudes, stainless steel exhibits a cyclic hardening behavior. The Ramberg-Osgood model fit the skeleton curve well and the simulated curves agree fairly well with the test curves. Therefore, the hardening parameters and cyclic constitutive parameters which calibrated by the test data can be applied to the structural seismic analysis, and improve the accuracy of analysis for the stainless steel structure under earthquake.