The utility model discloses a flange joint auxiliary device relates to flange joint technical field, makes the gasket fixed during flange joint, makes things convenient for staff's installation, improves staff's the work efficiency and the installation degree of accuracy. This flange joint auxiliary device includes: base member, base member include the direction part that extends to the second endfrom first end along the rectilinear direction, the correcting member, the correcting member includes portion of sliding and location portion, a sliding connection in the part that leads of sliding,location portion is used for the messenger portion of sliding to be fixed for the part that leads, and the portion of sliding includes the holder, and the holder is partial for the direction to extenda preset length to presetting the orientation, presets the partial extending direction of orientation perpendicular to direction, and the holder lies in the portion of sliding and moves towards one side that the partial second of direction was held, clamping piece, clamping piece set up in the second end of direction part, and the clamping piece extends the 2nd preset length for the direction part to presetting the orientation, and the surface of clamping piece is relative with the holder.