Abstract: Effect of mixing silicon with phosphate in different proportion on the forms of inorganic phosphorus was studied through cultural experiment in drab soil. The results show: In the day of culture, the translation of the available phosphate and Ca2-P reduces rapidly, but the translation of Ca8-P, Ca10-P, O-P, Al-P, Fe-P increases in the days from 0 to 20. Along with time extension, the drop trend of the content of the available phosphate and Ca2-P slows down, the content of Ca8-P and Al-P continues to increase, the content of O-P and Fe-P begin to drop, the content of Ca10-P does not change. Comparing the treatments of mixing silicon with phosphate in different proportion with the treatments of only phosphate, the content of the available phosphate and Ca2-P and Fe-P decreases. The content of Al-P and O-P increases. In the treatments of mixing silicon with phosphate in different proportion, the raising of the proportion of silicon with phosphate can make the available phosphate and Ca2-P and Fe-P and Al-P and O-P to reduce, the content of Ca8-P increase, and has little effect on Ca10-P. The experiment indicates: mixing silicon with phosphate cannot improve the available of P, but reduce the available in drab soil.