Abstract: In order to optimize the technological parameters of the 12000kg/h horizontal threshing line of four-stagethresher and eleven-classifier, the correlations of threshing quality and strips yield with throughput, moisture content and temperature of tobacco before threshing, and technological parameters of threshing line were analyzed on the basis of accumulated QC data.The results showed that:1) with the increase of throughput, the percentage of fine (<3.18mm) changed as a curve of "U" shape, the values of stem in lamina and lamina in stem increased accordingly;2) the share of strips over 12.7mm increased and that of below 3.18mm and the value of lamina in stem decreased with the increase of moisture content and temperature of tobacco before threshing within a certain range; and 3) with the increase of the share of strips over 12.7mm, the tobacco degradation and the value of lamina in stem reduced, and the strips yield increased, however, the value of stem in lamina would increase as well.