Abstract: The effect of heat treatment temperature on the microstructure transformation of the steel side in TA2-Q235B explosive clad plates was studied by optical microscopy (OM), electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM), and the formation mechanism was also analyzed. During the heat treatment process, the interface structure of the steel side decarburized, and a decarburized layer which is comprised of ferrite without structure characters formed. At 850℃ and below, the interface structure of the steel side near the swirl of the wave tip developed abnormally into big ferrite. At 900℃ and above, the interface structure of the steel side unusually grew into a columnar-structure ferrite structure. These aforesaid structures are influenced by both carbon diffusion and the phase transformation of matrix microstructure in the steel side. During the heat treatment process, TiC generated on the interface unevenly distributed on the interface, and locally accumulated on the interface with the increase of temperature, which accelerates the diffusion of carbon to the interface.