Abstract: It is difficult to predict the mechanical properties of welded joints because of nonlinear in welding process and complicated mutual effects in multi-composition welding material. Based on these practical problems, the application of neural network technology in predicting mechanical properties of welding joints is developed.The modeling method has been studied and the author puts forward that the parameters of neutral network can be optimized by the method of uniform design. The neutral network model of mechanical properties of welded joints is established on the basis of the data of welding thermal simulation, the experimental results show that this model can predict the mechanical pronerties include impact toughness, tensile strength, subdued strength,reduction ratio of area and hardness more accurately. At the same time, using this method can improve estimating precision largely compared with using traditional statistic method. That is, this method can provide an effective approach to estimate the mechanical properties of welded joints.