Abstract: T-joint of 4mm-thick CLAM steel was welded by 4 kW Nd:YAG laser welding equipment with different incident angles.Forming,distribution of residual stress and hardness are observed and analyzed.The result show that there is significant lack of fusion in the joint when the incidence angle is 14° and the joint fully fuses when the angle is 12° or 10° with the decreasing of incidence angle.The residual stress of the joint surface is compressive stress,the stress of flange is larger that of web when the angle is 12°.But the stress of web is larger when the angle is 10°.Inner stress largely changes in the section of the weld joint,compared with base metal,the hardness of weld zone has significantly increased and HAZ is not softened.