The invention discloses a phthalonitrile modified benzoxazine and epoxy resin composite material, preparation and an application. According to the invention, phthalonitrile modified benzoxazine and epoxy resin are composited, and the hthalonitrile modified benzoxazine and epoxy resin composite material is a novel high-performance thermoset polymer composite material; phenolic hydroxyl groups produced through benzoxazine curing not only can be taken as a phthalonitrile curing catalyst, but also can be taken as an epoxy resin curing agent, through synthetic curing of phthalonitrile, benzoxazine and epoxy resin, the crosslinking density of the material is further increased, and properties such as thermal oxidation stability, radiation resistance, high temperature resistance, flame retardancy, corrosion resistance, low water absorption property and the like are further improved, so that the material has excellent comprehensive performance to attract broad attention and is taken as high-performance resin material for wide application in the high-technology fields such as electronic industry, aerospace and the like. According to the monomer preparation method, the synthesis period is greatly shortened, raw materials for monomer synthesis are cheap and easily available, the preparation method is simple and convenient, and the yield is high. The related processing technology of the composite material is simple, and the performance is good.