In order to predict the dynamic characteristics, the piezoelectric valve-less diffuser micropump is equivalent to the hydraulic model which consists of several hydraulic components. Using finite element analysis (FEA) method, the static analysis and the natural frequency calculation of the diaphragm are carried out. The mathematical model and the simulation method using AMESim are developed. Simulation results show the pressure and flow rate characteristics of the micropump, as well as the diaphragm stiffness influence. The agreement between the simulation results and those published previously indicates that the method combining FEA with the hydraulic analogue model provides a relatively simple and effective tool to study the dynamic characteristics of micropumps.