Abstract: A numerical calculation model with local refined mesh for laser deep penetration welding of titanium alloy is presented. A Rotatry-Gauss body heat source model was established to accurately describe the shape of keyhole and molten pool of the laser welded joint. The profile of keyhole and molten pool as well as the distribution of high gradient residual stresse are obtained. It is showed that the region of high stress locates in the keyhole region, and high gradient residual stress distributes in the other region of welded seam. The stresse gradient increases in the state of excessively high and low level of energy density as well as the state of lower linear energy. It is supposed that keeping the laser energy density in state of low and medium level or keeping the linear energy in state of low level could avoid the high gradient stresses.