The invention discloses an offshore oil platform underwater cable disconnecting and reconnecting method and equipment. The method includes an offshore oil platform underwater cable disconnecting method and/or an under water reconnecting method. The method is short in work period of disconnecting and reconnecting an underwater cable, and is simple in process operation, use of professional well drilling equipment and consumption of massive manpower and material resources are not needed. The underwater cable disconnecting and connecting equipment comprises a sealing device used for sealing an upper end of the underwater cable, lowering rigging and an underwater robot, the lowering rigging comprises a first rigging component connected with the upper end of the underwater cable, a second rigging component detachably connected with the first rigging component and a third rigging component connected with the first rigging component, and the underwater robot is used for disconnecting or connecting the first rigging component and the second rigging component. The method is simple and convenient to operate, operation can be performed without various professionals, and simple and quick underwater cable disconnecting and reconnecting can be realized.