Abstract: The existing inorganic spray air leakage sealing materials are prone to cracking and forming air leakage cracks. Modifying the fibers containing non-polar groups and adding them to cement-based materials can effectively reduce the occurrence of air leakage cracks. To explore the surface modification effect, mechanical properties and reinforcing effect on spray materials of polypropylene (PP) fibers, hydrogen peroxide and catechol were used to modify the fiber surface. The surface morphology, Zeta potential and contact angle of the fibers were studied when the mass concentration of hydrogen peroxide was 0, 5 and 10 g/L and the modification time was 0, 6 and 12 h. The stress and elastic modulus of a single fiber, as well as the pull-out force, shear strength and pull-out energy of the fiber in cement-based materials were studied by using quasi-static and dynamic loading tests. The plugging air leakage rate containing different fiber materials was measured by using a plugging air leakage test device. The results show that the optimal modification conditions are hydrogen peroxide at 10 g/L and the time is 6 h. Compared with the unmodified fibers, the equipotential points of the hydrogen peroxide and catechol-modified fibers are present at 3.31-3.46. After modification under the optimal conditions, both the forward contact angle (θ_adv=58.1°) and the backward contact angle (θ_rec=34.9°) of the fiber surface were the smallest. After modification, the tensile strength peak value of a single fiber increased by 67%, the elastic modulus increased by 50%, the shear strength increased by 310.9%, and the pull-out energy increased by 354.2%. The plugging air leakage rate of the specimens with modified fibers added after compression was 98.5%. The mechanism of fiber modification is that the free radicals on the surface of catechol can undergo polymerization reactions under the action of hydrogen peroxide. The resulting polymer layer increases the roughness of the fiber surface, and at the same time, catechol decomposes to produce carboxyl groups. The polymer layer containing hydroxyl and carboxyl groups attached to the fiber surface and the increase of its surface roughness jointly enhance the tensile strength of the fiber and the mechanical properties at the interface with cement-based materials.