Abstract: The method of thermal simulation has been used to study the performance of the HAZ of the 07MnNiCrMoVDR steel. The microstructure and the performance are different under the different welding condition, and the coarse grain zone of HAZ is the worst region of low temperature toughness.Under the small heat input (10 KJ cm)and a higher preheating temperature (180℃)better performance can be attained.In addition, linear regression method was used to establish the forecast formula of performance, and the MATLAB was also used to optimize the welding procedure by the low temperature toughness optimal solution as the objective function.The small heat input and the high preheating temperature are the best protessing parameters.