Abstract: Conducting the method of typical investigation to collect 172 profiles of thesoil in the main Ph.pubescens stands in Zhejing and Fujian Province,633 samples of soil havebeen tested to analyse the available Si content.As a result,1.Contents of available Si in different soils vary because different kinds of rock,types of soil,geography(different of latitudes,or altitudes etc.).The soil available Si content is quite low in general igneous rock except for granite and tuff of higher elevation in this investigations,and is comparatively high insedimentary rock.But in metamorphic rocks it appearss in random.The order of the avail-able Si content in each kind of soil in order is:mountain yellow earthcalcareous soilmountain yellow-brown earthmountain red earth≥yellow-red earthacid purple soil≥low hill red earth.It indicated that the distribution of the soil available Si has a rising latitu-dinal zonality law of from the south to the north and a rising vertical zonality law of the altitudes from the bottom to the top.2.Average of soil available Si content in that area are:45.13 mg/kg(A horizon),76.56 mg/kg(B horizon),and its degree of variation Was thelargest.A distribution map of low available Si content regions in that area has been madebased on the cluster analysis