Abstract: One piece of Q345R steel plate (thickness 95 mm) fractured during coiling process in one chemical machinery plant. The fracture reason was analyzed through macroscopic inspection, chemical compositions analysis, mechanical properties test and metallographic inspection. The results show that burrs on surface layer produced in the process of gas cutting groove were not clear away before coiling, and over burning, carburizing and quenching cracking layer were remained. The crack expanded quickly under the action of external force in coiling process, and eventually led to the fracture of the Q345R steel plate.