Abstract: Choosing the reactions of hydrogenation of CO and CO_2 as two key reactions of methanol synthesis, the mathematical model of multiple-stage quenching-with-feed-gas type methanol synthesis reactor has been established. With the aid of global kinetics equations of domestic C301 Cu-based catalyst and using direct searching method, the optimun design, making the volume of the catalytic beds minimum at given production capacity, has been made. When the volume of the reactor has been given at the different catalyst ages, the opti- mun operating conditions making the production maximun have been found.