This paper reports on the parametric study of a diffuser geometrical design for different opening angle, curvature ratio and velocity flow profile using finite element modeling (FEM) approach. The coupling effect of the designed diffuser with the actuator response is experimental studied, where two resonant peaks of the flow rate and back pressure at 2–70 Hz operating frequency are observed. The first peak occurs when the driving frequency is tuned to the natural frequency of actuator, whereas the second peak is due to the net flow characteristic of the diffuser. The experimental study is further extended to analyze the effect of the membrane thickness to the dynamic performance of the micropump. From the experiment, shifting of resonant frequency is noted when thinner membrane is utilized. The study provides a comprehensive guideline for the design parameters of a diffuser element.