To accurately describe the constitutive relationship of the corroded steel under cyclic loading， the mechanical properties and degradation rules of the corroded steel were obtained through the monostatic tensile and cyclic loading tests on 16 groups of corroded Q355 steel specimens subjected to artificially accelerated corrosion. The influence of corrosion on the hysteretic properties of steel specimens was analyzed， and a cyclic constitutive model of corroded steel was established based on Giuffre-Menegotto-Pinto （GMP） model. The results show that the yield strength， ultimate strength and corresponding yield strain， ultimate strain and other mechanical properties of steel show a linear degradation trend with the increase of corrosion degree； corrosion weakens the energy consumption capacity of steel， making it difficult to ensure the safety of the structure under reciprocating loads； the cyclic constitutive model of corroded steel is in good agreement with the test results， which can provide support for the seismic performance evaluation of steel members and structures in corrosive environments.