The invention discloses a barium sulfate crystal assembly line quantitative filling device. A material loading bag to be filled is placed on a flexible plate by an operator, the edge of a bag opening of the material loading bag is sucked by a pore machined in the flexible plate, and then the material loading bag is conveyed to the position under a weighing barrel through a conveying belt. Barium sulfate crystals in a material supply tank fall into the weighing barrel in the meantime until a measured value of a weight sensor reaches a designated value. Meanwhile, a piston rod of a jetting air cylinder pushes out a nozzle forwards, the material loading bag is opened after high-pressure gas is ejected by the nozzle, then the barium sulfate crystals in the weighing barrel fall into the material loading bag, and the bottom of the material loading bag makes contact with the conveying belt. After filling is completed, the material loading bag is conveyed to the next procedure through the conveying belt, and so far the filling operation of one material loading bag is completed through the barium sulfate crystal assembly line quantitative filling device. According to the barium sulfate crystal assembly line quantitative filling device, the barium sulfate crystals can be bagged, the efficiency is high, the action process of the device is smooth, the operation is completed automatically, and the physical output of the operator is reduced.