Methanol is one of the three most important products of the chemical industry in the world and many substances are derived from it. Also, due to the predictable shortage of energy resources in the future, the direct use of methanol as a clean fuel or in the production of hydrogen used in fuel cells is very important. In the present work, we have investigated the radial-axial flow reactor of methanol production, which is the newest type of methanol synthesis reactor, and instead of using the old shell and tube reactor, the shell and plate reactor has been used. In addition, the fluid flow in the reactor is both axial and radial, so that in the first 70 cm of the catalyst bed, the flow is axial, and in the continuation of the bed, the gas flow flows radially. In saturated steam plates with a temperature of 460 K to cool the reactor, it flows and in the gas shell passes through the catalyst bed and the reaction takes place. The plates are located on two rings around the center of the reactor and the catalysts are located between these plates. Our aim in this study is to simulate a three-dimensional radial-axial reactor by computational fluid dynamics method and compare it with industrial data. Also, to improve the performance of the reactor, we propose two designs and review and compare the results with the radial-axial reactor. In the first design, instead of two rings of cooling plates, a series of rings were used for the plates, thus reducing the number of cooling plates and saving costs and water consumption. In the second scheme, in the outer ring, instead of the flow of saturated water vapor, we passed the feed stream through the cooling plates in order to preheat. The results showed that in the new design reactor, because the temperature in the reaction medium is higher than the radial-axial reactor, the production of methanol is also 3% higher. In the new design reactor, due to preheating of the feed stream, methanol production increased by 2% and water consump