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Potato harvest mechanization is the weakest link in the whole mechanized production of potato, in which stem and leaf chopping is an important part of potato mechanized harvest. Stem and leaf chopping has the advantages of accelerating the separation of potato seedlings and tubers, promoting potato epidermal hardening, reducing disease transmission, reducing epidermal damage and missing harvest during excavation, which can effectively reduce the loss rate of mechanical harvest per unit area. At the same time, potato stem and leaf crushing can effectively avoid potato seedling winding operation machinery, reduce the working load of harvester, improve the reliability of machinery, improve the operation speed of harvesting machinery and increase soil fertility. Aiming at the problems of low qualified rate of breaking length, high potato carrying rate and slow working speed of the active potato stem and leaf chopper, a full ridge imitation form of stem and leaf chopping knife roller was designed, the working process of the cutter was analyzed, the mathematical models of cutter movement, cutter stalk collision and stalk picking were established, and the main parameters and value range affecting the working performance of the device were determined, and the overall structure of the full ridge imitation and the design of stem and leaf chopping knife roll were completed. Using the three factor five level quadratic regression orthogonal rotation center combination test method, the field test was carried out with the operation speed, knife roller speed and the height of knife roller from the ground as the test factors, and the qualified rate of broken length and potato belt rate as the evaluation indexes. The test data processing and parameter combination optimization were carried out with the software Design-Expert 8.0.6.1. The results showed that all factors had a significant impact on the qualified rate of broken length. The primary and secondary relationships from large to small were the rotation speed of knife roller, operation speed and the height of knife roller from the ground. Each factor had a significant impact on the potato carrying rate, and the primary and secondary relationships from large to small were the height of knife roller from the ground, the rotation speed of knife roller and the operation speed. When the rotating speed of the knife roller was 1450r/min, the operating speed was 3.5~6.7km/h and the distance from the knife roller to the ground was 285~317mm, the qualified rate of breaking length was more than 90% and the potato carrying rate was no more than 0.3%. The research results can provide design theory and feasible technical support for improving the operation quality and efficiency of potato stem and leaf chopping machine.