The invention relates to a U-shaped isothermal low-pressure methanol converter with new support ring, comprising a outer cylinder, and inner elements, wherein, said outer cylinder comprises a upper closure head, a cylinder body, a positioning ring, and a lower closure head; and said inner elements comprises a separation plate, a cold gallbladder, and a support ring, while said upper closure head has a charging pipe; said lower closure head has a discharging pipe; the air guiding pipe of cold gallbladder is sealed on the separation plate with stuffing and catalyst is arranged outside said cold gallbladder; the cold gallbladder pipe is in multiple rings U-shaped and via support ring supported on the positioning ring welded on the inner wall of outer cylinder to hang and support cold gallbladder; the support ring has positioning hole to through ascending-descending cold pipe and several big holes to contain catalyst; said outer cylinder also comprises a air distributor inside the upper closure head to connect the charging pipe. The invention provides a new U-shaped isothermal low-pressure methanol converter with uniformly distributed charged air, high synthesizing efficiency, simple structure and lower producing cost, which can apply large methanol synthesizing device.