Abstract: The oil stored in cavern has a big free fall, and the flowstate of fluid within the inlet pipe is special. The improper design may trigger the fall pipe vibration from water hammer, negative pressure cavitations, gas-liquid mixture and a series of problems. Based on the hydrodynamic condition analysis of big fall pipe, energy equations were applied to hydraulically calculate and demonstrate a cavern case. Results showed that in the instability process of "empty pipe" under the condition of running, inertia head of the fall pipe played a role of "resistance", which consumed the residual energy in the fall pipe. In a stable production process, to properly reduce the diameter of big fall pipe, install a horizontal tube with a certain length at the bottom of the fall pipe and set up some energy-consuming components are reasonable and effective disposal technology to speed up the energy consumption.