Fuzzy PID controller was applied in variable air volume system. The task was to control the temperature of supply air and the temperature of airconditioned room (the return air temperature) close to their respective targets. The fuzzy PID control system of supply air temperature and return air temperature was designed respectively. The supply air temperature was controlled through adjusting the valve opening of chilled water. And the indoor temperature was controlled through adjusting the rotational speed of variable frequency ventilator. The supply air temperature and the indoor temperature (return air temperature) were controlled online by fuzzy PID controller. Thus

it was shown that the design of fuzzy PID controller was reasonable and the effect of fuzzy PID control was well.