The invention discloses a preparation method of a phenolic resin impregnation glass fiber composite material. The preparation method comprises following steps: heat treatment, acid etching, and coupling agent treatment are adopted for surface treatment of glass fiber; the treated glass fiber is immersed in a boron modified phenolic resin alcoholic solution obtained via modification with zirconium boride of a certain concentration, vacuum impregnation is carried out, an obtained product is delivered into a muffle furnace for curing molding, an obtained primary product is delivered into a phenolic resin alcoholic solution of a certain mass concentration for repeat impregnation curing so as to obtain a finished product. Optimization of the preparation method is carried out a series of property characterization, and the phenolic resin impregnation glass fiber composite material with desirable density is obtained finally. The advantages of the phenolic resin impregnation glass fiber composite material are that: the density is as low as 0.25 to 0.4g/cm3, excellent oxidation resistance is achieved, the preparation method is simple; and the phenolic resin impregnation glass fiber composite material can be used in the field of high temperature thermal protection.