The invention provides a method for repairing a jacket on the sea. According to the method, the following repairing steps are adopted: 1, detecting the jacket; 2, determining a jacket repairing scheme; 3, repairing the damage to the waterborne part of the jacket; and 4, repairing cracks in the underwater part of the jacket in a dry cabin. The method provided by the invention has the advantages that when being confronted with a defect on the sea, the jacket can be repaired through a cutting-replacement method; when the underwater part of the jacket is subjected to a critical defect, welding construction personnel can be allowed to directly enter the dry cabin and perform defect repairing operation on the jacket; not only can the problem that the jacket is difficult to repair when being confronted with the defect on the sea be solved, but also the problem that the jacket needs to repair when being confronted with the defect below the water can be solved; and accordingly, the efficiency of construction on the sea can be greatly improved.