The freezing and thawing action is an important factor affecting the form and transformation of soil inorganic phosphorus, which is an essential element of ecosystem. In order to examine the changes of inorganic phosphorus fractions and their efficiency under freezing and thawing conditions, a black soil was selected, and the inorganic phosphorus fractions and their efficiency were measured with the method of Jackson and Zhang Shoujing under indoor simulation conditions. The results showed that the absolute contents of inorganic phosphorus fractions increased generally after freezing-thawing, while the relative content of inorganic phosphorus did not change significantly. The contents of inorganic phosphorus fractions followed the order: O-P>Fe-P>Al-P>Ca-P. Correlation analysis and path analysis indicated that Al-P and Fe-P were the available phosphorus source and affected the content of soil available phosphorus directly; while O-P, Ca-P and Al-P had larger coefficient of size chain, indicating that O-P and Ca-P indirectly affect the available phosphorus content through their interactions with Al-P. A good linear relationship was observed between Olsen-P( Y) and Al-P (X₁) and Fe-P (X₂).