The author studied 9 chemical compositions of moso bamboo aged from 1 to 8 years and the differences of chemical composition in the different parts of culm were studied.The results shown:ash content varies by quadratic equation,and lignin increases with bamboo ages by exponential equation,but the other chemical compositions show a periodical change with aging.According to the variation regularity of chemical compositions the bamboo mature growing can be classified as three periods:increasing period(below 4 years old),steady period(5～7 years old),declining period(above 8 years old).The difference of main chemical compositions in the different parts of the culm is very little though the kinds of abstracts of bamboo decline a little from the bottom to the top.