Underwater mounting portal of deep water expansion bend

An underwater mounting portal of a deep water expansion bend comprises two vertical bearing beams symmetrically arranged at the bottom, and a transverse bearing beam mounted at the tops of the two vertical bearing beams, wherein a plurality of diagonal braces are mounted between the vertical bearing beams and the transverse bearing beam respectively; a plurality of lugs for allowing a chain block to penetrate through are mounted on the vertical bearing beams and the transverse bearing beam respectively; anti-settling plates absorbed onto a seabed are mounted at the bottoms of the vertical bearing beams respectively; and a portal frame for underwater mounting of the deep water expansion bend is formed via the connection. The portal has the benefits that the portal facilitates manual operation of a diver to lift an expansion bend flange underwater when the expansion bend flange is lifted in deep water; the lifting process becomes operable, safe and controllable; the expansion bend flange can be lifted more safely and efficiently; and the problems of great site operation difficulty and lower working efficiency due to increased water depth of a task are solved.