Affected by phase shifts,the transvers e intensity distribution (TID) of high-power blending mode CO 2 laser beam wi ll changed regularly in different position along its propagation path.This will influence laser welding greatly.The beam studied in this paper is of high-power blending-mode CO 2 laser beams whose mode composition are,TEM 00 :2 0 % about,TEM 02 :80 % about.In different processing position of flying op tics,the TIDs of focus will present concave and convex profiles.These two kinds of profile influence differentially on the keyhole formation,flowage of molten p ool and shape of welding seam in laser welding.It is shows from our research tha t the welding quality of convex profile is better than that of concave profile,a nd more small umbilicated degree of concave profile,more better laser welding qu ality.