55% pirimiphos-methyl EC mixed ultrapure water by proportion of 1∶2, was sprayed to the surface and the upper space of grain in large warehouse by Ultra-low-volume sprayer. Our study was performed twice at the end of April 2019 and the end of July 2019 respectively. Stored-grain pest protection layer was formed on the surface of grain bulk to continuously prevent the grain from suffering pest infringement. At the same time, the temperature controlled by air conditioner of warehouse was lower than 25 ℃. In this way, we can maximize the effect of pirimiphos-methyl protective layer on insect pests. By using pirimiphos-methyl will significantly reduce the amount of aluminium phosphide used in large warehouse and the intensity of labor. Because of the low toxicity, residue, cost and environmental friendly of pirimiphos-methyl, we concentrate on replacing aluminium phosphide with pirimiphos-methyl to achieve the goal of warehouse fumigation-free all year round.