In this paper, simulation of dynamic characteristics of pneumatically driven micropumps is presented. SPICE was used as a system level simulator. The SPICE model employed equivalent electrical circuit parameters extracted by an energy based calculation method. The thickness, side length of the diaphragm and forward resistance of valves were selected as variable to study the effect of design parameters in the performance of micropumps. Since the flow and pressure response of micropumps are similar to those of a differential electrical circuit, two parameters, namely, maximum amplitude and time constant of the system were used to discuss the simulation results. The results are of fundamental important to the understanding and optimization of the micropump.