Abstract: A coupling flange assembly for connecting steel pipes including coupling flanges having stiffening plates located on the front side of the flange plate along axial directions of the steel pipes towards a coupling surface of the steel pipe to be connected. Equilibrium contact surfaces are set up on front end surfaces of the stiffening plates. Two abutting coupling flange assemblies may be used to connect two steel pipes, and when the two steel pipes are connected, the equilibrium contact surfaces of each stiffening plate of the coupling flange assemblies will be in contact with each other on a one-to-one basis.