The invention relates to a quantitative casting system for casting. The quantitative casting system comprises a steel structure quantitative bag, wherein a refractory layer is arranged on the inner wall of the quantitative bag; the bottom of the quantitative bag is provided with a water gap; a vertical carbon rod is mounted in the quantitative bag; the bottom of the carbon rod is plugged in the water gap; a lifting device is connected on the carbon rod; the lifting device comprises a screw, a slide rod and a balance frame, wherein the screw is coaxially connected to the top end of the carbon rod through a protective sleeve; a lifting rope is connected on the protective sleeve; two slide rails which form vertical guide are mounted on the outer wall of the quantitative bag; the slide rod is connected in the slide sleeves in a penetration manner; the top end of the slide rod is fixedly connected to the top end of the screw through the horizontal balance frame; the bottom end of the slide rod is provided with a safety blocking head which is limited in the slide sleeves in a lifting process; a groove-shaped seam is formed between the safety blocking head and the slide rod; a spring clip is arranged on the bottom of the inferior slide sleeve; and the spring clip is matched with the seam.