The invention relates to an aerobic composting reactor and belongs to the technical field of composting fermentation. The aerobic composting reactor is characterized by comprising a tank body, a stirrer, sensors and a control monitoring module; a flange cover is arranged at the top of the tank body; the flange cover is provided with a feeding port and an exhaust port; a water bath jacket is arranged on the outer wall of the tank body; the stirrer consists of a stirring motor, a shaft coupler and a stirring paddle; the stirring motor is connected with the stirring paddle through the shaft coupler; a stirring shaft is arranged in the center of the tank body; the tank body is provided with a pH sensor, an oxygen sensor, a temperature sensor and a moisture sensor; the control monitoring module is connected with the pH sensor, the oxygen sensor, the temperature sensor and the moisture sensor; and the control monitoring module controls the stirring motor, the water bath jacket, a gas inlet and a gas inlet control mechanism. The aerobic composting reactor can improve the mixing uniformity of materials in the tank, maintains temperature distribution and oxygen concentration distribution in the tank to be uniform and constant, and controls the composting fermentation condition and performs real-time monitoring easily.