A control method of a driving circuit is provided for controlling a piezoelectric actuator of a piezoelectric pump to move a fluid of a fluid reservoir. Firstly, a driving voltage is outputted from the driving circuit. Then, a first inhalation adjusting process is implemented while the piezoelectric pump performs an inhaling operation. In the first inhalation adjusting process, a fluid pressure of the fluid within the fluid reservoir is detected and the fluid pressure is adjusted to the first predetermined inhalation pressure value according to the detecting result. Then, a first exhalation adjusting process is performed while the piezoelectric pump performs an exhaling operation. In the first exhalation adjusting process, the fluid pressure is detected and the fluid pressure is adjusted to the first predetermined exhalation pressure value according to the detecting result.