Abstract: Nd:YAG Laser heat-conduction welding is one of important laser welding mode which is applied to welding of thin parts.Study on temperature field is a common method to study welding process because it is one of direct token of welding process.In this paper,3D analytical mode of laser heat conduction welding is studied.Bond line dimension is calculated based on the 3D model.In the end,the model is verified by comparing the dimension of tested bond line with that of calculation.The comparative results indicate that the model can calculated the bond line,and theoretical results are identical with that of experiment.