The utility model relates to a diameter of axle is to isothermal reactor, including the casing that is equipped with gas access and gas outlet, the first barrel in the casing is established to the cover, and the second barrel in first barrel is established to the cover, has airflow channel between first barrel and the casing, support piece goes up and lies in between first insulating layer and the second septum thermosphere including the first barrel setting, and the equipartition has a plurality of intercommunication airflow channel and a cylinder?cavity's inlet port on the lateral wall of first barrel, the interval is equipped with a plurality of gas collection holes on the lateral wall of second barrel, and the last port of second barrel seals, lower port intercommunication the gas outlet, still be equipped with at least one cooling unit in its characterized in that reaction zone, pipeline, cooling unit's exit linkage output pipeline is imported to cooling unit's entry linkage refrigerant. The utility model discloses can in time remove reaction heat, effective controlled reaction district temperature for the reaction is gone on towards the positive direction, and the pressure drop can effectively be avoided to the feeding to the diameter of axle simultaneously, the unsettled problem of having solved the thermal energy that sets up of reaction zone.