Abstract-Gas-liquid mixing pump is one type of microbubble generator which is very efficient for mixing gas and liquid directly and dissolve them. However, one of the problems in designing the rotating machinery is the vibration, because the vibration is usually a direct cause of the component damage. In this paper, the dynamic characteristic of shaft system on a micro bubble generating pump was evaluated based on finite element analysis using ANSYS to investigate the stability and the critical speed of the system. Based on the results of evaluation, finite element analysis can predict the vibration modes on the entire segment of the shaft system in accordance with the natural frequencies of the respective modes. However, it did not find any critical speeds below the design rotational velocity of the shaft system. It can be concluded that the shaft system of the gas-liquid mixing pump was still outside the resonance region and the structural design of the shaft system could be operated safely.. Index Terms-Finite element, Campbell diagram, natural frequency, micro bubble, gas-liquid mixing pump.