A three-dimensional model is developed for numerical analysis of the temperature and stress fields in wire filling laser multilayer welding on high strength steel of 16 mm in thickness by the MARC software. During the calculation, with the technique of element birth and death, the Gaussian cylindrical heat source of heat flux linear attenuation and the double ellipsoid heat source are used to simulate the keyhole effect and the filler wire heating process, respectively. Predicted results are in good accordance with the experimental data. The results show that interlayer heat insulation can effectively reduce the cooling rate of the welded joint and decrease the residual stress, which improves the properties of welded joint. The stress concentration is mainly located in the lower part of the weld; the groove tends to shrink in welding and the work piece exhibits a certain angular distortion after welding.