The invention provides an improved combined sealing ring. The improved combined sealing ring comprises a metal sealing ring body and two nonmetal sealing ring bodies symmetrically located at the two ends of the metal sealing ring body, and is characterized in that a fixing groove is formed in the center of the outer side of the ring wall of the metal sealing ring body, and the fixing groove is symmetrically and sequentially provided with grooves and sealing faces towards the two ends, wherein the grooves are used for containing the nonmetal sealing ring bodies, and the sealing surfaces are used for achieving sealing in cooperation with flanges; the two nonmetal sealing ring bodies are placed in the grooves which are formed in the metal sealing ring body and used for containing the nonmetal sealing ring bodies. The improved combined sealing ring can be disassembled and replaced by an artificial robot under water, the process of collecting the sealing ring and the flanges to the land for replacement is avoided, operating time is shortened, and operating efficiency is improved; automatic and precise butt joint of the combined inner and outer pressure sealing ring can be achieved under the action of pretightening force of the flanges, so that the whole sealing ring bears large applied load, the problem of sealing failure caused by overlarge inner pressure is solved, engineering safety is guaranteed, and engineering quality is improved.