The invention discloses a nitrile resin monomer, a nitrile resin polymer and a preparation method of the nitrile resin monomer and the nitrile resin polymer, belonging to the technical field of organic polymer materials. The nitrile resin monomer is a tetraphthalonitrile resin monomer containing benzoxazine cycle, and the nitrile resin polymer is a product obtained by heating polymerization of the nitrile resin monomer. The nitrile resin monomer has a low viscosity, a good mobility and the processing performances of low-temperature curing and the like at a low temperature. The nitrile resin polymer has the good curing performances of self-flame resistance, adhesion, heat stability and the like. The resin monomer has the good processing performances of benzoxazine resins, and the resin polymer has the high-temperature resistance of nitrile resins, thus reducing the curing processing temperature and being capable of being used in a high-temperature temperature, namely, having the advantages of low temperature processing, medium temperature formation and high temperature use; and the resin monomer and the resin polymer can be used in the fields of coatings, adhesives, electronic packaging materials, aeronautics, astronautics, ships, resin matrix composites and the like. The preparation method is simple and easy to control, low in reaction temperature, energy-saving, and suitable for industrialized production.