The invention provides a protective device for a sea floating structure and relates to the field of oceaneering protective equipment. The protective device for the sea floating structure comprises connection structures and at least three buoys. The at least three buoys are in the hollow cylindrical shape and are distributed evenly around the sea floating structure. Ballasts are arraged in all the at least three buoys. The at least three buoys are connected with the sea floating structure through the connection structures correspondingly. The connection structures can adjust the distance of the at least three buoys and the sea floating structure. According to the protective device for the sea floating structure, the technical problems that in the prior art, protective equipment for a sea floating structure is large in implementary difficulty, high in cost and poor in mobility are solved.