Aiming at the problems that potato stems trash separation was ineffective during the potato harvest, potato harvest potato stem separation equipment was designed under the condition of heavy soil in northern China. Based on the kinematics analysis of the potato stems during lifting process of device and the analysis of force during the separation process and elastic mechanics analysis during the separation process, an elastic mechanics model was established, the main factors affecting the separation effect of the yam were determined, and the picking roll speed affecting the separation performance was obtained. Taking the distance between the line speed, picking roll and the main driving roller of the first-stage lift separation screen as the test factor, and the field test was carried out with the impurity-containing test index. The test results showed that when the distance between picking roll and the main driving roller of the first-stage lift separation screen was 2.5mm, the rotation speed of the picking roller was 9.0r/s, and the linear speed of the main driving roller of the first-stage lifting separation screen was 1.6m/s, the impurity content was 2.4%, and the index was superior to the national industry standard. The research result provided an important theoretical support and reference for both large combine harvesters and segmented potato harvesters, and also provided important theoretical support and technical reference for the separation of potato and potato stem during potato mechanical harvesting.