Abstract: A cascade of spherical reactors can be used in the large scale methanol synthesis process under low pressure, because of simplicity of manufacture and flexibility of operation, where one methanol synthesis converter is divided into several reactors in series. The one -dimensional heterogeneous model of the spherical reactors is presented, which describes the distribution of gaseous compositions and temperatures in the gas bulk and on the external surface of the catalyst particle. The effectiveness factors of the parallel hydrogenation reactions of carbon monoxide and carbon dioxide to methanol over Cu - based catalyst were calculated by the orthogonal collocation method. The volume of the spherical fixed bed and the optimal operating conditions were found out by the Powell optimization method.