The effects of the addition of several supercritical media on the equilibrium CO conversion in the methanol synthesis based on syngas under supercritical conditions were calculated by using the Soave-Redlich-Kwong equation of state. The results showed that the addition of proper solvents such as n-hexane and n-heptane could improve the CO conversion greatly under supercritical conditions. When using n-hexane, the favorite solvent mole fraction was 0.2-0.3, the optimum temperature was in the range of 473-483 K, and the pressure was above 8 MPa.