Abstract: A computational fluid dynamics model named the centrifugal acceleration model for simulating gas-liquid two-phase flow in a shake flask was proposed. The model was successfully applied to investigate effects of baffles, rotation speed and filling volume on the mass transfer and shearing environment in the shake flask flow field. The results show that the presence of the baffle increases the gas-liquid oxygen transfer capacity inside the flask and provides a larger shearing environment than the unbaffled flask; Higher rotation speed is favorable for the gas-liquid mass transfer ability, and the optimal liquid volume exists for a specific rotation speed that provides the best gas-liquid oxygen mass transfer capacity. Finally, the flow field simulation results were analyzed for interpreting the better result for clavulanic acid seed and fermentation process in baffled flask. The method formed in this paper can be extended to the fermentation analysis of other products.