The invention discloses a coating material applied to the surface of a PBO (Polybenzoxazole) fiber. The coating material is prepared from an ultraviolet absorber, heptadecafluorodecyl trimethoxy silane, organosilicon-modified epoxy resin, a curing agent and an organic solvent. Besides, the invention also discloses an application method of the coating material. A coating is prepared by mixing a mixed solution of the ultraviolet absorber, the heptadecafluorodecyl trimethoxy silane and isopropanol with an organosilicon-modified epoxy resin solution; the ultraviolet resistant performance of the PBO fiber treated by the coating is greatly improved; after accelerated aging for 400 hours, the retention rate of fiber strength is improved by 50 percent; in addition, the hydrophobicity of the PBO fiber is substantially improved, and a water contact angle of the PBO fiber can reach 130 to 140 degrees. After the PBO fiber is treated by the coating, the service life of the PBO fiber is greatly prolonged, and the water resisting property of the PBO fiber is greatly improved.