Atmospheric pressure continuous flow microplasma reactor was developed for the fabrication of silicon nanocrystals in gas phase. Mixture of argon, hydrogen, and silicon tetrachloride (SiCl4) was activated by non-thermal plasma generated in a capillary glass tube with a volume of less than 1 micro-liter. A microplasma reactor provides high-density reactive media where silicon precursor is efficiently decomposed into atomic silicon even though residence time is shorter than 10-100 micro s. Supersaturated silicon vapor gives rise to gas phase nucleation via three-body collision, followed by rapid termination of crystal growth due to short residence. time reactor. Silicon nanocrystal is thus obtained without post annealing process. Room temperature photoluminescence (PL) excited by He-Cd laser (325 nm) exhibited intense visible emission with peak intensity around 700 nm. The PL spectrum of as-grown sample was blue-shifted down to 540 nm with increasing hydrogen content; implying nc-Si core and oxide shell structures with core diameters of 1-3 nm. Green-liminescent silicon nanocrystals blue-shifted until 450 nm after natural oxidation in air.