The invention relates to a range hood automatic control method and system based on multi-sensor fusion. The range hood automatic control method comprises the steps: real-time temperature data, real-time humidity data and real-time oil smoke concentration data nearby a range hood are obtained, and control coefficients, for a range hood air damper, of the temperature, the humidity and the oil smokeconcentration are calculated; according to all the obtained control coefficients, for the range hood air damper, of the temperature, the humidity and the oil smoke concentration, the influence coefficient, for the range hood air damper, of the environment air condition is obtained, and according to the identification result of whether a human body is located nearby the range hood or not, the finalinfluence coefficient, for the range hood air damper, of the human body is obtained; and a preset gear threshold value aiming at the gear of the range hood air damper is set according to the final influence coefficient, for the range hood air damper, of the human body, and according to the preset gear threshold value, the air damper gear corresponding to the range hood is obtained. According to the range hood automatic control method and system, influences of the temperature, the humidity, the oil smoke concentration and the human body factor on gear control of the range hood are sufficientlyconsidered, and through fusion processing of the various environment factor influences, the gear of the range hood air damper is real-timely and accurately controlled.