In view of the problems of unstable measurement, large packaging damage and low packaging efficiency in the quantitative packaging of potato quantitative packaging machine in China, the principle of S-type tension sensor was used to weigh, and the weighing accuracy and stability were improved. On this basis, the structural design of quantitative packaging device was carried out. The structural parameters were determined by analyzing the key components of the quantitative packaging device, and the key factors affecting the packaging performance and the range of values were clarified. Taking conveyor belt speed, drainage plate angle and bagging height as experimental factors, weighing qualified rate, peeling rate and potato injury rate as experimental evaluation indexes, with the help of software Design-Expert 10.0.3, three factors and three levels experiments were carried out by Design-Behnken, and the experimental results were analyzed by variance analysis. The influence of various interactive factors on the experimental indexes was analyzed by response surface test. The structure and working parameters of the quantitative bagging device were optimized, and the optimal value of each factor was determined according to the actual working conditions. On this basis, five quantitative packaging tests were carried out on the test bench. The verification test showed that when the speed of the conveying line was 0.44m/s, the angle of the drainage plate was 62.3°, and the packaging height was 496.1mm, the qualified rate of weighing was 97.32%, the rate of skin breakage was 1.22%, and the rate of sweet potato injury was 0.94%. Compared with the theoretical value after parameter optimization, the relative errors between the measured value and the theoretical value were 1.23%, 2.40% and 2.17%, respectively. It was shown that the quantitative bagging device improved the qualified rate of bagging, improved the efficiency of bagging and replacement, and reduced the damage of skin and potato.