Abstract: When the arc force is strong,the double ellipsoid heat source model is the most widely used heat source model. The influence of the heat source parameters on the weld size was researched,and the sensitivity of the double ellipsoid heat source parameters was obtained for SAW. The multiple regression analysis was applied to research the relationship between the weld size and the heat source parameters. An empirical formula was put forward,and the heat source parameters corresponding to the weld width and penetration can be easily calculated by the empirical formula. The trial time is reduced and the simulation precision is increased.