Aiming at the problems of low precision and low automation in quantitative feeding of granular agricultural products, the physical characteristics of common granular agricultural products were analyzed. A quantitative method based on volume estimation of mass was adopted, and a closed-loop control scheme was introduced into the control system. A dynamic quantitative feeding equipment for granular agricultural products was developed. The equipment mainly consisted of a quantitative device with a variable volume measuring cup structure, a transmission and distribution mechanism, and a reinspection weighing scale. Based on the explanation of the mechanical structure and working principle, a closed-loop control algorithm based on historical discrete data fitting prediction error was proposed. When the reinspection process detected a difference between the feeding quality and the target quality, the volume of the measuring cup in the quantitative feeding process would be compensated and corrected through a closed-loop control system, thereby reducing the error of quantitative feeding. The results of experiment showed that the equipment could achieve high-precision dynamic quantitative feeding of granular agricultural products with anti-interference and adaptive capabilities. Taking rice, soybeans, and kidney beans as the experimental object, the feeding quality error could be stably controlled within 1% after three sets of closed-loop feedback adjustments when the rotational speed of the turntable was 4r/min. And the quantitative accuracy was far higher than that of the national requirement for the allowable shortage of quantitatively packaged goods.