Abstract: At present, the damage rate, loss rate and impurity rate of grain mechanized harvesting are high due to the improper configuration of threshing and separating device and improper adjustment of operation parameters. In this paper, the development and research status of domestic combine harvester are summarized. The advantages and disadvantages of threshing and separating device of combine harvester are discussed from the aspects of threshing principle, structure and key components. The problems of low working efficiency, high total loss rate, high impurity rate and complex structure of threshing and separating device of combine harvester are discussed In order to improve the efficiency and performance of combine threshing and separation system, and gradually realize informatization and intelligence, combined with the current research status, the development trend of threshing and separating device of combine harvester is put forward, so as to provide reference for the improvement and optimization of combine structure in China.