The invention discloses a preparation method of a boron-containing pyrolytic carbon coating on the fiber surface. The preparation method comprises the steps that fibers are soaked in a boride-containing phenol-formaldehyde resin sizing agent, curing is conducted, high-temperature heat treatment is conducted, and the boron-containing pyrolytic carbon coating is obtained on the fiber surface, wherein the boride-containing phenol-formaldehyde resin sizing agent is prepared from, by mass, 0.5%-8% of boride, 0.5%-8% of phenol-formaldehyde resin, 0-1.6% of curing agent and the balance solvent. According to the preparation method of the boron-containing pyrolytic carbon coating on the fiber surface, by means of soaking and pyrolysis, the boron-containing pyrolytic carbon coating with uniform thickness is introduced on the fiber surface, the boron-containing pyrolytic carbon coating serves as a reinforcement body to prepare a ceramic based composite material, and toughness and oxidation resistance of the composite material can be improved simultaneously. The preparation method is simple, economical and suitable for industrial production.