The present application provides a reactor with an inclined bottom gas-inlet for aerobic fermentation. A fermenter is provided with a circular inner tank, end covers and a jacket. An airtight fermentation space is formed in the fermenter by the inner tank, an upper end cover and a lower end cover. A feed opening and an exhaust outlet are arranged at an upper part of the fermenter, and a discharge opening is arranged at a lower part of the lower end cover of the fermenter. An energy-saving stirrer is mounted in the fermenter. A plurality of air chambers are arranged at an external wall at the bottom of the inner tank of the fermenter and are within the jacket. A plurality of aeration nozzles are defined on an inner side of each air chamber, and the aeration nozzles are disposed next to the inner tank.