Abstract: The surface of waste rubber powder (WRP) grafted with acrylic acid (AA) was performed under the inducing of ultraviolet (UV) using benzophenone (BP) as photosensitizer. The fabrication parameters were optimized via orthogonal method. The modified WRP/natural rubber (NR) composites were fabricated. The surface morphology and structures of WRP before and after modified, and the effects of WRP content on the mechanical properties of WRP/NR composites were studied. Results show that the highest grafting degree of 3.38% was gained in the optimized condition with 10wt% AA, 9wt% BP, 150 μm grain size of WRP and 4 min of illumination time. The rougher surface of modified WRP was observed when compared with the unmodified samples. The tensile strength and Shore A hardness were increased first, and then decreased with the content of modified WRP increased, and the peak values (27.28 MPa and 69.2 HSA, respectively) were obtained when 10wt% WRP added.