Micro gas pump is one of the important micro fluidic components, which can be used for gas analysis in chemical, air supply of micro fuel cell and micro fluid cooling systems. Pumping gases requires a strong compression ratio inside the pump chamber for gas could be compressed. This paper presents a micro diaphragm air pump actuated by PZT bimorphs, which characterizes thin structure, large air flow and low power consumption. The diaphragm air pump is made up of a cavity and an actuating structure. The actuating structure consists of two PZT bimorphs and a diaphragm with check valves, which could produce large volumetric change ratio. Then, a prototype of the pump whose cavity's dimension is 60×16×2mm was fabricated by precise manufacture. The mathematical models were established and simulation had been carried out, in which the parameters, such as flow rate, diaphragm's vibrating amplitude and resonant frequency are calculated and analyzed. Furthermore, experiments on the pump were carried out. The experimental data are basically agreement with the simulation results. With a voltage of 20V, the air pump's flow is 85.3ml/min in resonance and its power consumption is only 3.18mW. Simulations and experiments show that the diaphragm air pump has high efficiency and good performance. It also shows good application prospects in air supply for micro fuel cell and micro electronic devices' cooling.