Changes of chemical composition, crystallization, and morphology of laser synthesized amorphous Si/C/N nanocomposite powders during heat treatment under nitrogen and argon were investigated. The influence of nitrogen and argon on the chemical composition and crystallization of the powders were different. when the temperature exceeded 1750 degrees C, however, the amorphous Si/C/N nanocomposite powders were transformed into pure crystalline beta-SIC powders under either nitrogen or argon. The particle sizes of the nanometric powders increased abruptly as increasing the annealing temperature and reached micrometer scale above 1750 degrees C.