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.