The utility model relates to a cut deal box post especially relates to cut deal box post butt joint interface. A butt joint interface is fixed a position fast to cut deal box post, treats between upper prop and the lower prop of butt joint to include with socket joint formula interface connection: it sets up upper and lower baffle separately to be close to the kneck in upper prop and the lower prop, a pair of side along a pair of extension plate of welding of lower prop, draw forth a pair of plugboard near another group's opposite side is inboard from last baffle in the upper prop, this plugboard is followed insert between the extension plate, weld between its end and the lower prop port and seal, extension plate and the welding of upper prop port are sealed. The utility model discloses can be used for the installation accuracy deviation of adjusting the structure, guarantee that the mother metal is not impaired.