Electric field-induced point electron source is highly demanded for microscopy, spectroscopy, lithography, X-ray tubes, microwave devices, and data displays. However, the instability in emission current and requirement of ultrahigh vacuum have often limited its extensive applications. Herewith we report a single-crystalline HfC nanowire with oxycarbide emission surface for stable electron emission at 50 nA with fluctuations less than 1% in a vacuum of 4 × 10^-7 Pa. The emitter has a low work function of 2.5 eV measured by the field emission Fowler-Nordheim curve and it is in good agreement with density functional theory (DFT) calculations. The energy spread is in a range of 0.21-0.26 eV with a corresponding reduced brightness 1.95 × 10¹¹-3.81 × 10¹¹ A·m^-2·sr^-1·V^-1. The HfC nanowire with oxycarbide emission surface is a qualified candidate for the next-generation electron source with high brightness, large current, and low energy spread.