Salt cavern is one of the significant types of underground gas storage. During the construction of the salt cavern gas storage, part of the insoluble particles will remain in the cavity. The insoluble particles gradually deposit in the bottom of the salt cave, which reduces the cavity construction speed and lessens the volume of gas storage. The high-pressure rotating water jet technology is simulated to flush insoluble particles, and the flushing system is mainly composed of surface facilities and downhole flushing tools. The seven high-pressure rotating water jets can flush the insoluble particles at the bottom of the cavity. A mathematical model with the solid-liquid two-phase flow is established and numerical simulated first. Then, this paper analyzes the influence of the injection flowrate, the distance from inlet to outlet, the rotational velocity on the flushing efficiency. The results show that the injection flowrate and the distance from inlet to outlet are the two main controlling factors. Under the conditions of this paper, the injection flowrate is 100 m³/h, the rotational velocity is 300 r/min~400 r/min, the distance from inlet to outlet is between 0.5 m~1.0 m, and the flushing efficiency is higher than that of other range studied. The research is helpful to understand the flushing rule and optimize the flushing parameters during the construction of the gas storage through water jetting technology.