The utility model provides a novel device is changed in maintenance of offshore platform crude oil riser, coupling assembling including water proof cabin and a plurality of group link water proof cabin and offshore platform spud leg, the bottom in water proof cabin is equipped with the through -hole that a confession crude oil riser runs through, still include the sealing member, the sealing member is including the rubber seal section of thick bamboo and the rubber seal frustum that set gradually, the diameter of the last bottom surface of rubber seal frustum is lighter than the diameter of bottom surface down, a rubber seal section of thick bamboo connects with the less upper base facial features of diameter of rubber seal frustum, the sealing member is equipped with the inner chamber of through -going shaft to the both ends face, the lower bottom surface and the through -hole of rubber seal frustum are connected. Novel device is changed in maintenance of offshore platform crude oil riser, enable water proof under -deck portion and sea water and keep apart, prevent that the water proof cabin from intaking, when water proof cabin below and fixed mounting, convenient operation is and can guarantee staff's construction safety.