The as-cast Mn18Cr18N electroslag remelted steel was directly rolled in a single pass, and the reduction rates were 10%, 30%, 40% and 50%, respectively. The microstructure was observed by electron backscatter diffraction system (EBSD). The results show that the microstructure is gradually refined with the increasing of reduction rate in rolling with single pass. Recrystallization occurs around the grain boundary. The increasing of deformation twins promotes recrystallization nucleation. The structure refinement is dominated by the dynamic recrystallization mechanism and the twinning mechanism. The tensile mechanical properties of rolled sheet were analyzed. As the reduction rate increases, the yield strength increases from 690.16 MPa to 743.24 MPa, the tensile strength increases from 885.65 MPa to 940.31 MPa, and the elongation after fracture increases from 39.73% to 53.46%. The fracture morphology feature gradually changes from mixed fracture of toughness and brittleness to dimple toughness fracture. The content of the second phase at the edges of fracture is relatively small, while the microholes in the center of sample contain a large number of square second phases, and it causes the formation of microcracks, and the fracture starts from the center.