The relationship between composition of stems and tillers and LAI was studied in high-yielding population (Shanyou 63 and Guangling Xiangjing).The results indicated that:(1)The ratio of LAI of tillers of 4 leaf-age and over 4 leaf-age at N-n and elongating stage was high in high-yielding population.(2)The ratio of number of total tiller of 3 leaf-age and 3 leaf-age at N-n and elongating stage was high in high-yielding population.(3)The number of total tillers of 4 leaf-age and over 4 leaf-age correlated significantly with the total LAI at elongating stage.