The vibration characteristics of piezoceramic bimorphs are studied on the solid-liquid coupled effect for the micro-pump devices. Resonant frequencies and mode shapes of piezoelectric elements, which promote flow in different fluids including air, water and glycerin, are obtained by experimental measurements and finite element numerical calculations. Two different piezoelectric micropumps are designed for verifying the solid-liquid coupled vibrations of piezoelectric bimorphs both on the fluid surface and under fluids. One of piezoelectric micropump uses a piezoelectric material bonding on the PDMS polymer, and the vibration in resonance produces the changes of chamber volume for increasing fluid flow. Another is the biomimetic design, which embedded piezoelectric material in the pump chamber, imitating fish tail swing for promoting liquids to flow. Piezoelectric bimorphs are investigated by using three experimental techniques obtaining the solid-liquid coupled vibration characteristics. First, the self-arranged vertically electric speckle pattern interferometry (ESPI) is used to measure simultaneously the resonant frequencies and mode shapes for the vibrations of piezoelectric bimorphs in the fluid. Second, the laser Doppler vibrometer (LDV) can obtain frequency spectrum of vibrating displacement by dynamic signal swept-sine analysis. Third, the correspondent resonant frequencies and anti-resonant frequencies in fluids are obtained by impedance analysis for the piezoelectric bimorphs. Moreover, the quadratic, three-dimensional piezoelectric-solid element and acoustic coupling element, respectively, are used to setup the piezoelectric device and different fluids in finite element method (FEM). All the experimental results are compared with the solid-liquid coupled vibration characteristics in FEM calculation. Finally, the two kinds of piezoelectric micropumps operate on the resonant frequencies to measure the flow rate in water. It has good consistence in resonant frequencies and mode shapes by experimental measurements and finite element numerical calculations.