Abstract: In this paper, the dynamic behaviors of molten pool in autogenous laser welding and laser welding with filler wire were analyzed by high-speed camera online monitoring system, and the appearance of weld was compared and analyzed.The dynamic behaviors of molten pool under the action of autogenous laser welding and laser welding with filler wire were further analyzed by numerical simulation.The results showed that the surface of the molten pool behind the keyhole wall in autogenous laser welding, the flow from the keyhole opening to the tail of the molten pool occurred, and the metal bulge appeared behind the keyhole opening. The size of the metal bulge was large, and the weld formation in autogenous laser welding was poor, and there were pits on the surface.The surface melt of the molten pool behind the keyhole wall in laser welding with filler wire flowed from the keyhole opening to the tail of the molten pool. But under the surface of the molten pool there was a flow from the tail of the molten pool to the keyhole. Although welding spatter would also occur, the size of welding spatter was relatively small, and due to the filling effect of liquid metal, the weld surface was not easy to appear concave defects, and the weld was well formed. Compared with the autogenous laser welding, the fluctuation of melt flow velocity behind the keyhole wall increased significantly after the liquid droplet entered the molten pool.