The invention discloses a method and a device for feedback control of the air quantity of a central air conditioner, which relates to a control technique for the central air conditioner. An existing air conditioner has an overlarge air quantity, wastes energy sources, blows hot and cold in turn and has a poor indoor comfort level. The method comprises the following steps of: 1) performing detection, namely detecting the air quantity at an outlet of a fan coil unit by a air quantity detection device, and measuring the indoor temperature by a temperature detection device; 2) performing air quantity calculation, namely, comparing the actual temperature with a set temperature to obtain the difference value of the actual temperature and the set temperature, and calculating the needed air quantity according to the temperature difference value; 3) performing air quantity compensation, namely, comparing the actual air quantity with the needed air quantity to obtain the difference value of the actual air quantity and the needed air quantity, calculating the rotating speed of a fan motor according to the air quantity difference value, and compensating the air quantity; and 4) performing regulation, namely performing the regulation according to the calculated rotating speed of the fan motor, and returning to the step 1) for circulation. The method and the device use a PI regulating unit to regulate the rotating speed of the motor so as to regulate the output air quantity, realize the double closed-loop control of the temperature and the air quantity, and achieve the effects of improving the comfort level and saving energy.