Abstract: Taking the medium and heavy plate Q345B produced by a steel factory as the research object, Q345B steel plate was rolled and descaled through different rolling temperatures and derusting passes, the structure and morphology of the surface oxide scale of the finished product were analyzed by scanning electron microscope (SEM), X ray diffraction (XRD) and energy disperse spectroscopy (EDS). The effect of descaling processes on the removal of iron oxide scale on the surface of the steel plate was studied, and the best descaling process was explored. The results show that the iron oxide scale produced on the surface of the steel plate in the four rust removal processes is composed of FeO, Fe₃O₄ and Fe₂O₃; In the subsequent finishing rolling process, adding rust removal passes, and the rust removal effect is not good due to the adhesion of iron oxide; The content of Fe₃O₄ and Fe₂O₃ produced in the first descaling process is high and the distribution is uniform, which is an ideal descaling process.