The present invention provides a liquid replenishing device comprising a liquid storage tank, a chemical liquid supply pipeline, an ultrapure water supply pipeline, an ultrapure water quantitative supplement pipeline and a circulating pipeline. The pressure vessel is intended for use in seawater desalination by reverse osmosis, and comprises a pipe body formed by filament winding, and is furnished with an occluding cover at each end of the pipe body, the peripheral surface of the pipe body being furnished, inward from the occluding covers, with inflowoutflow parts through which the fluid flows in or out. If the packaging station is fully utilized or stopped, the belt catch can be positioned such that the products can be placed in the store.