Abstract: Due to the low level of mechanized harvest of millet,there is still a big gap between the level of mechanized harvest of rice and wheat.Therefore,in view of the problems existing in the threshing and separating device of millet harvester,the test-bed of single axial flow threshing and separating device is developed in this paper.By means of single factor test and orthogonal test,the influence of drum speed,feeding amount and threshing gap on the quality of threshing and separation was studied by variance and range analysis,and the threshing performance of the device was verified.The results show that the main order of influence is drum speed＞threshing clearance＞feeding amount＞concave sieve bar spacing for the threshing rate and millet agglomerates rate;the main order of influence is threshing clearance＞concave sieve bar spacing＞feeding amount＞drum speed for the loss rate.The optimum parameters of the device are drum speed of 950r/min,feeding amount of 2kg/s,concave sieve bar spacing of 8mm,threshing clearance of 8mm.The results show that the threshing rate is 91.1%,the millet agglomerates rate is 8.1%,and the loss rate is 0.8%,which meets the national standard of grain harvest.