The relative densities of SiCl (n) (n = 0-2) in SiCl4 radio frequency (rf) glow discharge plasma are measured by mass spectrometry. The effects of discharge parameters, i.e., rf power, discharge pressure, substrate temperature, and SiCl4 flow rate on the relative densities of SiCl (n) (n = 0-2) are investigated in detail. An optimum configuration of discharge parameters (low rf power, high discharge pressure, low substrate temperature, and low flow rate), which enhanced the formation of SiCl (n) (n = 0-2) radicals, is searched by a great deal of measurements and discussions. In the optimum configuration of discharge parameters, we measure the spatial distribution of SiCl (n) (n = 0-2) radicals in the most optimized plasma parameters. The experimental results reveal that Si and SiCl may be the dominant precursors in forming the thin film.