Abstract: In order to research the relativity between main traits of leaves and yield of soybean under different planting conditions, this experiment took Kennong No.4, a variety of soybean, as the experimental material, established five different treatments and measured its three main trait indexes of leaves at five different growing period, they are the leaf dry weight, the leaf area index and the content of chlorophyll. The result of the test shows: on unit area land, three traits have the closely positive relativity with yield. The relativity between dry leaves weight, both colony middle and upper of every treatments at every periods, and yields attained remarkable even more remarkable level; The relativity between leaf area index and yield reached remarkable level at R1 period and R5 period, and the relativity between leaf area index and yield, at R6 period and the average of all growing period, reached more remarkable level; The relativity between yield and the content of chlorophyll a, chlorophyll b and chlorophyll(a+b) on unit area land at the period of R1 and R5.