A kind of automatic quantitative liquid filling machine mainly used for filling toxic and volatile liquid was designed. The control part includes bucket conveying, bunghole positioning and quantitative liquid filling and pailful of transportation and other work under PLC control. The measuring instrument is F701 weighing controller, which achieve precise weighing through PLC control. In the whole quantificational filling process, people are not needed to contact filling liquid. The machine will complete working process automatically. The hardware and software design of automatic quantitative liquid filling machine control system was introduced and analyzed in detail.