Single-crystal -Si3N4 particles with a quasi-spherical morphology were synthesized via an efficient carbothermal reduction-nitridation (CRN) strategy. The -Si3N4 particles synthesized under an N-2 pressure of 0.3MPa, at 1450 degrees C and with 10mol% unique CaF2 additives showed good dispersity and an average size of about 650nm. X-ray photoelectron spectroscopy analysis revealed that there was no SiC or Si-C-N compounds in the -Si3N4 products. Selected-area electron-diffraction pattern and high-resolution image indicated single crystalline structure of the typical -Si3N4 particles without an obvious amorphous oxidation layer on the surface. The growth mechanism of the quasi-spherical -Si3N4 particles was proposed based on the transmission electron microscopy and energy dispersive X-ray spectroscopy characterization, which was helpful for controllable synthesis of -Si3N4 particles by CRN method. Owing to the quasi-spherical morphology, good dispersity, high purity, and single-crystal structure, the submicro-sized -Si3N4 particles were promising fillers for preparing resin-based composites with high thermal conductivity.