Abstract: Based on simulating the cooling process of carburized large gear rings during quenching in ANSYS software,the map of temperature ftield during the quenching was obtained,and the maximum temperature difference between the workpiece and fixture in the plastic temperature zone was determined.The temperature difference,specially designed fixture and the work of metal high-temperature plasticity and transformation plasticity made the gear ring become round by itself while quenching.Thus the process to make the ring round by press could be eliminated after heat treatment and advantages of the quenching process such as less distorsion,high production efficiency,low cost and less crack etc is exhibited.