By the SiC particle tracer method, the effect rule of filler wire on the surface flow of molten pool is obtained, and the effects of different welding processes, wire feeding modes and wire feeding angles on the fluctuation behavior of the molten pool surface and weld formation are analyzed. The results show that, in the autogenous laser welding process, the liquid metal on the molten pool surface flows to the back and the other side of the molten pool, the molten pool surface fluctuates remarkably, and depression defects appear on the weld surface; in the laser welding process with filler wire, the molten pool surface metal flows rapidly from forward to backward, the molten pool surface is relatively stable, and the weld surface is well formed. In the process of laser welding with filler wire, the transition modes of filler wire have significant effects on the stability of the molten pool surface, and it is beneficial to obtaining a stable liquid bridge transition and reducing the weld hole defects by reducing the wire feeding angle.