In order to realize the automatic packaging of powdery dangerous chemicals and improve the packaging efficiency, an automatic box closing device for powdery dangerous chemicals packaging bags was designed. According to the manual box closing process, the key devices were designed to realize automatic bag taking, bag opening, box closing and other functions. The working principle of the box closing device was analyzed, and the key parameters of the main mechanism were theoretically analyzed to provide a basis for its parameter selection. The production practice proved that all functions of the automatic box closing device for powdery dangerous chemicals packaging bags have been realized, with all components operating in coordination, and there was no relative movement between moving parts. The box closing device could replace manual operation and shorten the process cycle, which is of great significance to improving the automation of the powder dangerous chemicals packaging system.