The longitudinal axial threshing and separating unit and the tangential longitudinal axial combine harvester were used to conduct comparative experiment on spike tooth, combination of spike tooth and short rasp bar, short rasp bar and long rasp bar. The experimental results showed that the loss ratio before threshing and the threshing rate of short rasp bar were 4.58% and 95.38%, respectively. Comprehensive threshing and separating performance were better than other threshing units and could relieve cleaning load effectively.