Objectives The problems of easy air inlet and poor effectiveness of sealing in the use of silage methods including pits, bundled silage bags and wrapping in animal husbandry in the southern mountainous grasslands of Guanling County, Guizhou Province, were solved. Methods A large-scale flooded silage device with plastic bag was designed based on the principles of pressure difference between the connector and the level of liquid. The silage effect of the device designed was compared with that of the traditional bundled bag and silage pit. The quality of sensory, the effect of feeding, and the quality of fermentation in silage feed were analyzed. Results The device had one-way exhaust and complete functions of sealing, allowing stable storage of silage feed under anaerobic conditions. The color and odor of maize silage using a flooded device was significantly better than that of silage in bundled bag and pit. There was no mold on the surface, with pH of 3.85, belonging to the excellent grade. Cattle enjoyed eating it. Conclusions The silage device designed is not only beneficial for long-term preservation of feed, but also convenient for transportation, and reduction of cost and increase of efficiency. It is suitable for promotion and application in the southern mountainous areas of China, where the climate is hot, the humidity of air is high, and the terrain is rugged and complex.