Phyllostachys pracecox stands under intensive management different in history (1, 5, 10 and 15 years) in West Tianmu, Linan City, a major Phyllostachys pracecox production area, were selected for sampling of soil profiles, 0~10 cm, 10~20 cm and 20~40 cm, separately, in depth. These samples were subjected to sequential extraction for analysis of variation of contents and fractions of silicon with plantation age and soil depth. Results show that the content (0.084~0.318 g kg^-1) of available Si and its proportion (1.60%~12.3%) to soil Si in the profiles varied with the age of plantation and organic mulching, showing a curve downwards first and then turning rise . The content (2.58~5.15 g kg^-1) of amorphous Si and its proportion (75.1%~87.7%) in the topsoil increased with the age of plantation. Organic mulching promoted transformation of amorphous Si into available Si, organic Si and Fe/Mn-oxide Si. The findings of the study may be offered as reference for regulation of soil bioavailable Si in the soil of Phyllostachys pracecox stands.