As the sandwich panel structure is simple and relatively lighter with considerable strength,it has great application prospect in the shipbuilding industry. Using the laser welding to fabricate the steel sandwich panel is the preferred manufacturing technology.As the T-joint structure is the base welding unit of the sandwich structure,this paper has set up a T-joint welding platform based on laser welding. On the basis of the experimental results,a new mixed heat source model was proposed. The heat flux distribution during laser welding could be accurately described by the mixed heat source model. Through laser welding experiment and FEM calculation,the welding deformation and residual stresses of the sandwich structure were analyzed. Besides,the influence factors on the welding deformation and residual stresses were also discussed,finding that the welding deformation was significantly decreased by using laser welding,but the residual stress was still at high level.