Abstract: In order to predict the pressure pulsation in a piezoelectric valve-less nozzle/diffuser micropump according to fluid dynamics and cone tube characteristics, the dynamic mathematical models of the valve-less micropump are developed considering the mode continuity during supply and pump and the volume change of pump chamber. Using finite element method, the maximum volumetric deflection of vibrated diaphragm is calculated. Based on the micropump dynamic mathematical model, the pressure and flow characteristics are simulated to analyze the effects of maximum volumetric deflection of different diaphragm and vibration frequency on the dynamic characteristics of micropump. A piezoresistive micro pressure transducer fitted on the top of the chamber is used to measure the pressure pulsations in the pump chamber. A comparison between simulation results and experimental data shows that the micropump dynamic mathematical model is capable of predicting the pressure pulsations in valve-less micropump.