The invention discloses a hydrophobic coating material applied to a PBO (Poly-p-phenylene Benzobisoxazole) fiber surface. The coating material is prepared from organic silicon modified epoxy resin, (heptadecafluoro-1,1,2,2-tetradecyl)trimethoxysilane, an organic solvent and a curing agent according to a certain ratio. Furthermore, the invention further discloses a preparation method of a hydrophobic coating on the PBO fiber surface. One layer of thin film covers the PBO fiber surface treated by the hydrophobic coating material, so that the PBO fiber surface has a high hydrophobic property and a water contact angle can reach 140 degrees.