Abstract: According to the characteristics of weld shaping,the effect of the major laser welding parameters on weld shaping was investigated,and the differences between CO₂ laser and YAG laser fully penetrated weld shaping were compared.It showed that the cross section of both CO₂ laser and YAG laser fully penetrated weld of titanium alloy were typically of nail shape or near X shape,which was related to heat input and laser power density in welding.With increase of heat input and laser power density,the cross section of the weld transformed from nail shape to near X shape.And YAG laser weld of near X shape was more symmetrical than CO₂ laser weld with the same laser welding parameters.By adjusting the laser welding parameters,such as laser power,welding speed and focus position,the weld shaping could be controlled effectively and the welding quality could be improved.