The invention provides an underwater laser welding head provided with a movable gas hood. The underwater laser welding head provided with the movable gas hood comprises an optical cable (1), a sealing hood housing (2), a collimating mirror (4), a spectroscope (5), a wire feeder (6), a focusing mirror (8), the movable gas hood (9), a welding wire (10) and a vision module (11), wherein the sealing hood housing (2) covers the whole laser head; laser from an outlet of the optical cable (1) is converted into parallel light through the collimating mirror (4); the parallel light is collected at a welding position in the movable gas hood (9) through the focusing mirror (8); laser penetrates through the spectroscope, and visible light at the welding position is refracted to the vision module (11) through the spectroscope (5). The underwater laser welding head provided with the movable gas hood integrates the vision detecting, welding, wire feeding and other functions, is high in water sealing performance, and can be directly used underwater; argon is used for draining water and treated as protecting gas of the local gas hood, so that harmful influence of water invading a welding seam can be reduced, and the welding joint quality is obviously improved.