Among the wide list of known high performance polymers, polybenzoxazoles (PBOs) have gained a prominent position as the most heat-resistant polyheterocyclic polymer. Nonetheless, PBOs have found applications in a rather restricted variety of technologies, mainly in the form of fibers. Herein, we report our pioneering work for producing cross-linked polybenzoxazole via a novel route using recently developed smart class of benzoxazine resins as precursors. This class of benzoxazines incorporates multiple smart features all in one molecule. The most attractive feature is its structural transformation into a more thermally stable cross linked polybenzoxazole without the harmful consequences of traditional polybenzoxazole synthesis, such as the use of poly(phosphoric acid) as solvent By this smart conversion, the flame-retardant oxazole moieties. are successfully incorporated into the network structure. Further advantages of this new route for cross linked polybenzoxazoles include outstanding flexibility in molecular design, cost effectiveness, and easy processability.