Abstract: This paper summarizes progress in the development of models for calculating the flow of heat in welding.First,an analytic model which is most usually used as centralized point or line and face heat source was put forward.Then a mathematical model for weld heat source based on Gaussian distribution of power density in space was presented.Other models based on Gaussion distribution function were hemispherical power density distribution,ellipsoidal power density distribution,double ellipsoidal power density distribution.The computed temperature distribution in different models was compared and an opinion was made to select different model under different condition.It was shown that the analytic model was more simple and practical,it can be used in many projects.But it had some error near the pool for not considering the effect of penetration arc.The model of double ellipsoidal power density distribution can deal with both the shallow penetration arc welding processes and the deeper penetration laser and electron beam processes and make the calculated value more accurate.