Abstract: We take the laser beam energy as a line heat source to analyze the temperature field distribution T=(p/hν)/2(πεcρt)1/2exp-y2/(4αt) of the deep penetration laser welding,and emphasized the relation Bh=√2(πe)(1/cρTm)(p/v) of the welding speed v,and the depth B and width h of the welded seam.The experimental results show that the theoretical analysis are well agreement with practical operation.