The chemical equilibrium compositions and equilibrium constants of methanol synthesis reactions, starting from carbon monoxide, carbon dioxide and hydrogen, were studied experimentally at P=4.0-6.6MPa and t=220 approximately 260-degrees-C. It was found that lower temperatures and higher pressures are favourable to chemical equilibria in the interested range of the synthesis reactions using low-pressure process, but the influence of temperature on K(P) is much larger than that of pressure.