To study on the solid-liquid coupling vibration of slurry storage tanks of medium consistency pulp conveying system, a simplified finite element model was built with ANSYS code. Inherent vibration analysis of storage tank was analyzed by reduction method, and the first 30 modes of storage tank were extracted. The results indicated that the most modes of the tank showed multiple circumferential waves, the shaking range of medium consistency pulp suspensions was rather weaker at the core then around edge. Compared with the theoretical formula, the numerical calculation result was reasonable. It may provide for further analysis of dynamic response of the tank.