Abstract: Hot rolling strip steel Q215 steel after being treated by reduction was rolled by cold rolling of five passes using a four-high rolling mill. The morphology of surface and cross-section of samples after reduction and different passes of cold rolling was observed using scanning electron microscopy. The results show that the defects such as cracks, bubbles and pores on the surface of test steel after reduction were eliminated in the following cold rolling. The cracks gradually decreased in width and were nearly close, but there were some traces of cracks on the surface of test steel after five passes of cold rolling and the space between cracks increased. The thickness of decarburized layer decreased with the increase of rolling pass. Surface morphology improved and surface quality enhanced constantly.