In order to transform cornstalk into fuel methanol, the optimum experiments of the methanol synthesis from the cornstalk syngas with domestic Cu-based catalyst C301 were carried out in a tubular-flow integral and isothermal reactor under pressure of 5 MPa. The experiments focused on optimization of temperature for catalytic reaction, the compositions of cornstalk syngas and entrance flow of syngas. The optimum reaction conditions of methanol synthesis from cornstalk syngas were obtained by experiments. The study provided the scientific and practical basis to the pilot scale test of methanol production from biomass (straw) gas.