The invention relates to a fireproof door composition structure capable of improving heat deformation. The fireproof door composition structure comprises a skeleton, an inner door plate, an outer doorplate, heat resisting materials and a clamping and fixing device. The heat resisting materials are arranged between the skeleton and the inner door plate as well as between the skeleton and the outerdoor plate. The clamping and fixing device locates the inner door plate and the outer door plate. The effect that when the clamping and fixing device for locating the inner door plate and the outer door plate is subjected to high heat, the inner door plate or the outer door plate disengaged from the heating surface can be automatically fused off, and the inner door plate or the outer door plate subjected to heat deformation is made to be automatically disengaged from the heat resisting materials is utilized, the heat resisting materials can be intact and undamaged to continue to resist high heat, thus heat deformation and the damage phenomenon of the skeleton and the door plate on the other non-heated side do not occur, and accordingly, a whole fireproof door can achieve the effects of improving the fireproof strength and prolonging the fireproof time.