Abstract: The as-received material was subjected to obtain thermal circling curves of typical position by ANSYS software numerical simulation in the different welding technological parameters on 20 mm thick plate to optimize welding process parameters and predict microstructures and properties for improving welding quality, compared with the simulation results and the experimental results in the same welding process conditions. It was found that the values of the thermal circling curves were close to the values measured; the simulation width of welding heat affected zone was basically the same as the measured values; the lath bainite was gradually reduced, the granular bainite increased and the grain size also became coarse from base metal to fusion zone.