In order to solve the problems of high impurity rate and high damage rate of sugar beet root in the complicated separation and conveying process of sugar beet combined harvester, a six-row sugar beet combined harvester with three-stage separation and conveying device was designed.The main structure and working principle of the device were described, and the key parameters were determined. Through the kinematic analysis of soil and sugar beet in the separation and transportation process and energy analysis of sugar beet in the collision process, the main factors affecting the impurity rate and damage rate of sugar beet were determined. The rotation speed of the dial plate, the line speed of the rod-type chain screen and the inclination angle of the rubber tail screen were taken as the test factors, and the hybrid rate and the damage rate were taken as the test indexes. The quadratic regression orthogonal rotation combination test was carried out, and the results were analyzed by using Design-Expert 8.0.6 software, and the regression equation of the test factors and each index was obtained. The influence of each factor on the evaluation index was analyzed intuitively by response surface. The optimized parameters were obtained as follows: the rotation speed of the dial plate was 100.0r/min, the linear speed of the rod-type chain screen was 1.4m/s and the inclination angle of the rubber tail screen was 39.0°. The verification test was carried out. The results showed that the rate of breakage was 3.4% and the damage rate was 2.6%.