We succeeded in the synthesis of single-phase beta-SiC nanoparticles via simple and low-cost high-energy mechanical ball milling of a silicon and graphite mixture at ambient temperature. The synthesis products were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The results show that starting graphite and silicon mixture reacted completely into beta-SiC nanoparticles with an average grain size of approximately 8 nm after being milled for 20 h, and the grain size gradually decreased as milling time increased from 20 to 60 h but remained basically unchanged above 60 h. The agglomeration problem of the beta-SiC nanoparticles synthesized by ball milling was resolved to a great extent by the introduction of 2 wt% NH4Cl to the initial Si-C mixture. Under 325 nm excitation, a stable and intensive broad emission peak at 387 nm was observed in the photoluminescence (PL) spectrum of the synthetic nanoparticles, and this emission shows an obvious blueshift of bandgap.