The thermostatic incubation experiment was conducted to study the effect of monosodium glutamate tail liquid on the inorganic phosphorus and soil pH in northern calcareous soil.The results showed that，after the application，the Olsen-P，Ca2-P，Al-P，Fe-P value in the treated soil with monosodium glutamate tail liquid were increased by 70%~120%，155%~288%，29%~42%，6%~10%，respectively,and Ca10-P was decreased by 7%~8%.After 60 days cultivation,the pH value decreased by 1.17~1.27 units compared with CK.To a certain extent,monosodium glutamate tail liquid also reduced the amount of P fertilizer transformed to invalid form,and improved the phosphorus validity.By correlation analysis and regression analysis,in the condition of application of monosodium glutamate tail liquid,the main components of inorganic phosphorus(Olsen-P)in the northern calcareous soil were Ca2-P and Fe-P,the regression equation was:Y(Olsen-P)=-18.724+1.173X1(Ca2-P)+0.905X4(Fe-P).