Abstract:The state of available Silicon content of main soils in northeast region was studied.The result showed that the available Si content of black soil and cinnamon soil are high, meadow soil and brown earth are medium and the least is alabic soil. The average content of each soil is 605. 1, 577. 5, 357. 0. 271. 3 and 149. 2mg/kg respectively. There is a significant positive correlation between available sillcon content and pH value and also clay content of soil.Under certain soil water condition, the silicon is in available form (soluble or active) absorbed by plant after silicon was applied within 30 days. The change of the content of available silicon is rare within 20 days and tend to decrease during 20～30 days after Si was applied. The content range of different forms of silicon is undefinite form of silicon>active silicon>soiuble silicon. There is a significant positive correlation between available silicon content and active silicon content (r=0. 8438* *, n= 16). and no correlataion between available silicon and undefinite form of silicon or soluble silcon.