Abstract: In order to optimize the quality of the blending module during threshing and redrying and to realize the precise utilization of cut tobacco, the chemical composition change patterns of different sizes of strips from different ecological areas in China separated by 6 pneumatic separators of the first stage threshing unit were systematically analyzed. The results showed that: 1) There were differences in the chemical composition of tobacco strips from flue-cured tobacco plants in different ecological areas separated by the first stage threshing unit. 2) The strip size had a significant impact on the contents of some chemical compositions. Large and medium sized strips exhibited relatively consistent chemical compositions, while the difference between the scraps and the overall raw material was the greatest. As tobacco strip size decreased, total sugar, reducing sugar, and the sugar-to-nicotine ratio gradually declined, while total nitrogen, non-nicotine nitrogen, and the nitrogen-to-nicotine ratio progressively increased. 3) The most significant changes in the relative ratio of chemical compositions with fixed base in ecological areas Ⅴ and Ⅵ indicated that there were significant differences in the quality of different types of tobacco strips in these two production areas. 4) The quality patterns of different types of cigarettes separated by each pneumatic separator indicated that, the difference between the quality of small tobacco strips and the overall raw material was small, while the difference between the quality of scraps and the overall raw material was large. Among them, the difference between the quality of tobacco strips separated by the number 3 pneumatic separator and the overall raw material was the largest. In terms of spatial distribution, the quality stability of different types of tobacco strips separated by the pneumatic separators in areas Ⅶ and Ⅷ was better than that in areas Ⅴ and Ⅵ. This study provides a practical reference for the quality control of formula modules and the utilization of differentiated tobacco strip resources.