In this paper, with electron backscatter diffraction (EBSD) and SEM, the microstructure evolution and fractography of bonded interfaces were analyzed at various reduction rates (0, 15, 30, 40, 50 and 60) %. A 06Cr13/Q345R explosive-welded composite interface of 50-80 μm was the impact area of explosive cladding where the grains of 06Cr13 and Q345R were both low-sized and uniform. Subsequent to hot rolling, the explosive-welding effect on the 06Cr13-side interface was rapidly weakened. Compared to the 06Cr13-steel side, the explosive-cladding effect on the Q345R-side interface was slowly weakened. A continuous orientation distribution occurred, which indicated that a continuous, dynamic recrystallization mechanism existed in the explosive-welded composite plate. In contrast, the dominant recrystallization-deformation mechanism was the discontinuous, dynamic recrystallization, taking place under the rolling deformation. Two peaks existed between the 30-% reduction rate and the 60-% reduction rate, and they were apparently at positions <15°and 50°-60°. As the rolling reduction rate increased, the two materials were significantly bonded together and the interface diffusion distances of the peaks and valleys decreased and tended to be homologous, whereas the composite interface fault was increasingly less apparent.