Methanol can be used as possibole replacement for conventional gasoline and Diesel fuel. In order to produce methanol, it is necessary to decompose biomass, including cornstalks, which is a raw material from agricultural residues. A promising route for processing cornstals is made cornstalks gasficated with thermochemical method to prepare the syngas,which has been conducted under a down-flow fixed bed gasifier. While the low-heat-value cornstalk gas produced in the down-flow fixed bed gasifier needs purified and a variety of technical procedures such as deoxygenation, desulfurization, catalytic cracking of tar and hydrogenation. In this paper, the catalytic experiments of methanol synthesis with cornstalk syngas were carried out in a tubular-flow integral and isothermal reactor. The effect of reaction temperature, pressure, catalyst types, catalyst particle size, syngas flow at entering end and composition of syngas was determind. The experimental results indicated that the proper catalyst of the synthetic reaction was C301 and the optimum catalyst size (phi) was 0.833 mm x 0.351 mm. The optimal operating temperature and pressure were found to be 235 degrees C and 5 MPa, respectively. The suitable syngas flow 0.9-1.10 mol/h at entering end was selected and the suitable composition of syngas were CO 10.49%, CO(2) 8.8%, N(2) 37.32%, C(n)H(m) 0.95% and H(2) 40.49%. The methanol yield is 0.418 g/g cornstalk. Moreover,the densities,state equation parameters and the total reaction heat Delta H(T, P), of methanol reacting system was calculated by SHBWR state equation under givern reaction pressure. The calculation results provided basic data for the design of the industrial equipments in which catalyzed synthesis of methanol from cornstalk gases is operated.