Abstract: Q345 steel/TWIP steel/Q345 steel laminated composites were fabricated by using a combined process of hot rolling and warm rolling, the influence of warm rolling reduction ratio (60%-85%) on the interfacial microstructure and mechanical properties of the composites was systematically investigated. The results show that after warm rolling, the Q345 steel side maintains its typical ferrite-pearlite dual-phase structure, while the TWIP steel side retains a single-phase austenitic structure. At a 60% reduction ratio, lamellar pearlite is formed near the interface in Q345 steel, whereas a large number of deformation induced twins are generated in TWIP steel. Meanwhile, the local misorientation of the TWIP steel side is significantly higher than that of the Q345 steel side. With the increase of the reduction ratio, the grains at both sides show pronounced grain elongation along the rolling direction, forming fibrous microstructure. When the reduction ratio reaches 80%, distinct shear bands appear in the TWIP steel side, accompanied by a sharp increase in dislocation density and the formation of dislocation cells, dislocation tangles and multiple twins. The microhardness of the TWIP steel side consistently surpasses that of Q345 steel, with both values exhibiting a monotonic increasing trend as the reduction ratio increases. As the reduction ratio increases from 60% to 85%, the tensile strength of the composites significantly improves from 1645 MPa to 1938 MPa, while the elongation decreases from 11.2% to 8.5%, indicating a gradual transition from ductile to brittle fracture mechanisms. This work elucidates the correlation between warm rolling parameters and the microstructure-property relationship in TWIP steel/Q345 steel composites, providing crucial theoretical guidance and technical support for optimizing the process of such composites.