Thermodynamic analysis based on first-principles calculations were performed for SiHxCl4-x (x = 0~3) to compare characteristics of these chlorosilanes. In the range of 600-1100°C, SiCl4 almost does not decompose, while SiHCl3, SiH2Cl2, and SiH3Cl decompose and generate SiCl2 as main radical species. SiHCl3 and SiH2Cl2 have 3.8 and 4.5 times higher SiCl2 equilibrium partial pressure than SiH3Cl at 600°C, respectively. SiH3Cl has lower equilibrium partial pressure of HCl than SiHCl3 and SiH2Cl2 by order level. Thus, it is expected that CVD using SiH3Cl gas is less affected by HCl reaction.