In this communication, we demonstrate nonmetal SiO(x) nanoparticles (NPs) can tailor few-layer graphenes (FLGs) into graphene nanoribbons (GNRs) and regular pieces with smooth edges. The tailoring of graphene is realized by the movements of SiO(x) NPs along the graphene lattice in the atmosphere of H(2), and the tailored trenches exhibit high selectivity of the crystallographic orientation compared to the reported metal NPs. The low tailoring rate and the long lifetime provide great potential for accurate control of the trench length or the length of the tailored GNRs. As a result, smooth GNRs with a length of several micrometers and a width narrower than 10 nm are obtained. A catalytic hydrogenation mechanism is proposed for the tailoring of graphene by SiO(x) NPs. These findings open up the possibility for atomically precise graphene device fabrication without metal contamination and indicate the potential catalytic activity of nonmetal NPs for the hydrogenation of carbon materials.