The fibre wall thickness of moso bamboo during their mature growing period was measured.The results showed that:(1)The fibre wall thickness increases with the position change from the lacuna to the outer culm part,then decreases a little.(2)The fibre wall thickness of the same layer’s vascular bundles was not notably different.(3)The fibre wall thickness in the correspond part increases as logarithm with aging,and the tendency is that the young bamboo grows fast,and 7yearold bamboo grows slow.