By using the self-designed threshing apparatus test- bed, single- factor tests of roller- speed and tooth- angle were carried out and the values of these two factors were obtained. On this basis, the three factors orthogonal test, including the speed of the roller, the mesh aperture and the thresh gap, was researched. The two factors regression experiment, including the roller speed and the thresh gap, was also studied. Optimum parameter combination of threshing apparatus was obtained. When the mesh aperture was 14 mm, tooth angle was 0°, thresh gap was 18.5 mm, roller speed was 927 r/min and roller length was 700 mm, the threshing loss rate was 2.71% and the trash content was 19.20%.