Abstract: Super plastic deformation experiments of low activated Martensitic steel with multiple times of constrained groove pressing (CGP) at 500 ℃ and 600 ℃ were carried out, and the effects of deformation passes on the microstructure and mechanical properties of the steel were studied. The results show that the average grain size of the steel is refined from 1.37 μm in the initial tempering state to 0.88 μm. The content of large angle grain boundary changes slightly. After deformation, obvious (121)012, （011）111 and (101)111 textures are formed in the steel, meanwhile, (213)111 textures are formed, the appearance of 112111 texture in the steel effectively improves the tensile property of the material, (012)021 textures are formed in ferrite, and the obvious 013〈113〉 textures are formed in third pass. Among them, the appearance of 112111 plane texture effectively improves the tensile properties of the material. The tensile strength and hardness increase significantly, and the elongation rate decreases slightly. After deformation at 500 ℃, the tensile strength increases to 693.01 MPa after first pass, and then decreases to 689.74 MPa after third passes, and the elongation decreases from 18.59% in the initial state to 12.13%. After deformation at 600 ℃, the tensile strength increases to 685.97 MPa at first pass, and then decreases to 679.30 MPa after third pass. The elongation decreases to 15.62% after third pass. The above results prove that molding deformation is one of the effective methods to improve the mechanical properties of low activation steels.