The invention discloses a method and equipment for underwater welding of a sacrificial anode based on friction stud welding, which are mainly used for replacement and maintenance of submarine pipelines and underwater structures of ocean engineering. The underwater welding of the sacrificial anode based on friction stud welding can be completed by a submariner or an ROV (remote operated vehicle). The friction welding is the fixed-phase welding type, and the influence on the welding process by the environment pressure is relatively small. In addition, when a deeper water area cannot be reached by the common submarine method, the welding at the water area with depth of several hundreds of meters to several thousands of meters can be performed by the ROV. The method has the advantages that the operation cost is relatively lower, the operation is simple, and a welding joint with high quality can be obtained.