Contents and optical properties of soil aggregates under long time no fertilization were studied in this paper.Results showed that the content of residual humin（HMr） decreased with aggregate size reducing.Among different size aggregates,the content of ion linked humin（HMi） extracted from 0.25～0.053mm was the lowest,and the HMi/HMc ratio of ＜0.053mm was the highest.The E4/E6 ratio of HMi declined with the deceasing of soil aggregates and the HMi molecular of ＜0.053mm had a big molecular mass,high condensation degree and complex structure.