Abstract: According to the character of the lap joint groove, the signal of the changing bulk of the column as the input signal was introduced into the mathematical model for the waving TIG welding of the lap joint groove, and the simulating model for the whole system accordingly was set up.Keeping the techniques parameters, the differences between the simulating results of this modeling, the traditional results which was made use of changing the height of the welding torch and the welding experiments results were analyzed and compared.It proves that the model reflectes the reality, and more accurate than the traditional ones.