The invention discloses a combined mold for a plane window frame. The combined mold comprises an upper mold, a lower mold and an inner mold; a groove is formed in the upper end of the lower mold; a first shaping surface is arranged on the groove wall of the upper part of the groove; a first through hole is formed in the center of the bottom of the groove; the inner mold comprises an ejecting rod which is inserted in the through hole and can be ejected upwards and a shaping tip which is located above the through hole and matched with the groove in shape; a second shaping surface is arranged onthe side wall of the upper part of the shaping tip; after mold closing, the first shaping surface and the second shaping surface are matched to form a rib cavity of a plane window frame forging; and the lower end surface of the upper mold, the upper end surface of the lower mold, the first shaping surface and the second shaping surface are matched to form a forging cavity of the plane window frameforging. The inner mold of the combined mold has both effects of forging shaping and ejection after forging, deformation of a web is avoided during ejection, split-body manufacturing is adopted at the rib cavity of a conventional mold, combined use is performed, and the combined mold has the advantages that demolding is smooth, a forging rib is filled, the forging is not prone to deformation during demolding and manufacturing is easy.