Abstract: The piezoelectric pump with valve regarding the phenomenon of abrupt output-decreasing with frequency-increasing (ODFI) is analyzed and researched. The research finds that it is wrong that the increase of the frequency results in the decrease of the amplitude of piezo vibrator is the leading cause for the phenomena of abrupt output-decreasing with frequency-increasing (ODFI). And the experiment has testified that the existing theory is incorrect. The model of lagging of valve that can be used to explained the cause for the phe-nomena of abrupt output-decreasing with frequency increasing is forward. With frequency increasing is forward. Meanwhile it mentions a new method to observe and develops new observa-tion device used to observe the phenomena of ODFI. It intro-duces the quantized valve--lagging coefficient, which can be used to evaluate and review the valve, and makes it as the goal function of optimal design of valve.

Key words: Lagging of valve, Optimal design, Piezoelectric pump, Pump, Valve