In recent years, the safety accidents in warehouses caused by fumigation and exhaust have attracted great attention by people from grain industry and society. But there are few literature reports on safety during fumigation and exhaust operation, which needs to be further researched and pay more attention. The concentration of phosphine both inside and outside of the warehouse were detected in real warehouse experiment during fumigation and exhaust operation to explore the effective safety protection distance and protective measures, in order to provide reference for strengthening safety precautions against the safety accidents, reducing or avoiding personal injury and economic loss. The results show that the safety protection distance is related to the concentration of phosphine gas in the warehouse (in the grain pile), and the fixed safety protection distance can not be used as the basis to judge whether it is safe or not. The concentration of phosphine must be detected before approaching the fumigation area.