The utility model discloses a mold-pipe connection flange for construction of an underground diaphragm wall. The mold-pipe connection flange is respectively arranged on two ends of a mold pipe, the central part of the flange is provided with a hollow cylinder body, and the height of the hollow cylinder body is identical to the thickness of the flange; and the surface of the flange is in a rectangular shape, the diameter of the hollow cylinder body is more than the width of the flange, and the flange is connected with the outer circumference of the hollow cylinder body. Each mold pipe section is connected together through the mold-pipe connection flange, the length of the entire mold-pipe section is changed to adapt to the construction of different wall bodies in different depths; and meanwhile, the shape and the size of the hollow cylinder body are identical to that of an inner pipe in the mold pipe, so that sand or concrete in the working process can successfully pass through the mold pipe. The mold-pipe connection flange is suitable for the connection of the mold pipe with the cylindrical inner pipe and can have dual function of connection and a passage in the high-efficient construction of the underground diaphragm wall.