Abstract: The relationship between Yield and leaf area index and their dry matter accumulation were studied by using two soybean cultivars which have high yield potency, under different population. This experiment taked Kennong No.4 and Kenjian No21, a variety of soybean, as the experimental material The result showed that the leaf area index changed on parabola under different population densities and the corre lation coefficients of yield with the leaf area index were tending to positive correlation on V3andR1, and was significant on R3、R5andR6. The dry matter accumulation were various in different growing period and the correlation coefficients of yield with the dry matter accumulation were tending to positive correlation on R3, and was significant on R5.The experiment also indicated that the later population of KJ21 still maintained high leaf area index and dry matter accumulation, which benefit for high population densities.