Abstract: In view of the present situation that large quantities of soybean varieties or lines in Shanxi soybean production area were difficult to adapt to mechanized harvesting, the bottleneck problem of mechanized harvesting, the height of bottom pod, was studied, to provide a theoretical basis for mechanized harvesting of soybean. By using the method of cluster analysis and correlation analysis, the variation law of soybean pod height was summarized with the regulation of planting density, and the dynamic relationship between the density and the bottom pod height and the related yield traits was analyzed. The results showed that 18 accessions of germplasm were divided into 3 categories by cluster analysis at the Euclidean distance OD=8.23: the first kind was medium branched soybean, the second was multi branched soybean, and the third was few branched soybean. The changing trend of the bottom pod height of different branch type varieties was different along with the increasing planting density. When the bottom pod height was suitable for mechanized harvesting, the best combination point of density and yield was that, the density of medium branched type was 140000/hm2 and 270000/hm2, the density of few branched type was 120000/hm2 and 270000/hm2. The density of multi branched type was 240000/hm2. The density regulates the bottom pod height, increases the yield, and makes the mechanized harvesting feasible.