Carbon-fiber-supported NiO catalytic filters for oxidation of volatile organic compounds were prepared by electroless Ni-P plating and subsequent annealing processes. Surface structure and crystallinity of NiO film on carbon fiber could be modified by post-annealing at different temperatures (500 and $650^{circ}C$). Catalytic thermal decompositions of toluene over these catalytic filters were investigated. $500^{circ}C$-annealed sample showed a higher catalytic reactivity toward toluene decomposition than $650^{circ}C$-annealed one under same conditions, despite of its lower surface area and toluene adsorption capacity. X-ray diffraction and X-ray photoelectron spectroscopy studies suggest that amorphous structures of NiO on $500^{circ}C$-annealed catalyst caused the higher reactivity for oxidation of toluene than that of $650^{circ}C$-annealed sample with a higher crystallinity.