The invention discloses a central air conditioner control method based on a self-tuning discrete PID algorithm. A timer is adopted for sampling the temperature of a coil pipe, the temperature of a room, the rotating speed of an EC motor and opening information of a proportional electromagnetic valve in a timed mode, filtering processing is carried out, and valid sampling values are obtained; the working state of a system is judged through changes of sampling information; then, according to a self-tuning coefficient table, a proportionality coefficient, an integral coefficient, a differential coefficient, the control weight of the EC motor and the control weight of the proportional electromagnetic valve, needing to be adjusted, are obtained through table look-up; a temperature deviation, an integral value and a differential value are worked out, and the rotating speed of the EC motor and the opening angle of the proportional electromagnetic valve are worked out through the coefficients obtained through table look-up; finally, the EC motor and the proportional electromagnetic valve are driven to reach required values. The EC motor and the proportional electromagnetic valve are controlled through the self-tuning discrete PID algorithm, namely the cooling capacity and air volume of an air conditioner system are controlled, the room can reach a set target temperature rapidly, and the system can keep running in the cooling capacity consumption and supplementation stabilization state.