β-SiC nanowires (SiC NWs) were modified by H2 and N2 plasma treatment for improving the field-emission (FE) properties. The FE property of SiC NWs treated by H2 and N2 plasma was significantly improved, their turn-on field and threshold field were 3.2 and 6.7 V µm−1 for a 10-min H2 treatment, 3.0 and 6.3 V µm−1 for a 20-min H2 treatment, and 2.8 and 6.0 V µm−1 for a 10-min N2 treatment, respectively, while SiC NWs treated by N2 for 20 min displayed poorer FE properties compared with untreated SiC NWs. The results of scanning electron microscope (FE-SEM), transmission electron microscopy, high-resolution transmission electron microscopy, selected-area electronic diffraction, and X-ray diffraction showed that the surface of the SiC NWs became rough, but their microstructure did not change after the plasma treatments. The point effect was proposed to explain the improvement of FE properties. A new, simple, and effective method for improving SiC NWs FE properties was discovered, and it may serve as a referential work for enhancing FE properties of other one-dimensional nonmaterials.