Abstract: Abstract: 【Objective】This study explored the effects of low-molecular-weight organic acids on the inorganic phosphorus fractions of typical temperate forest soils in order to test the potential of these acids to convert inorganic phosphorus into phosphorus available to plants. The results obtained can provide data for use in the restoration and reconstruction of degraded temperate forest ecosystems, as well as the improvement of soil phosphorus utilization. 【Method】The effects of different concentrations(10, 25, 50 and 100 mmol/L)of oxalic acid, citric acid, and acetic acid, as well as a control treatment(CK, distilled water)on inorganic phosphorus in the a layer of soil from four types of typical temperate forest(virgin Betula costata-Pinus koriensis forest, natural birch secondary forest, P. koriensis plantation, and larch plantation)were studied by using 120-day indoor incubation methods.【Result】 The three kinds of low-molecular-weight organic acids activated Al-P and Fe-P, and solidified O-P and Ca-P in Pinus koriensis plantation and larch plantation soils, with the effect of the acids ranking oxalic acid > citric acid > acetic acid. Citric acid and oxalic acid reduced the O-P content in natural birch secondary forest, and translated it into other inorganic forms of phosphorus. Overall, after the treatment of the four forest types' soil with low-molecular-weight organic acids, inorganic phosphorus could be transformed into Al-P and Fe-P with high availability, thus improving soil phosphorus supplying capacity to plants. Low-molecular-weight organic acids had significant effects on the change in soil inorganic phosphorus fractions(P < 0.05), and the magnitude of the changes ranked Ca-P > Fe-P > Al-P >O-P. Medium and low concentrations had the greatest impact on variation in Al-P, Fe-P, and O-P, and high concentrations had the greatest impact on variation in Ca-P. The treatment time had a significant influence on the change in inorganic phosphorus(P < 0.05). The effects on Al-P and Fe-P in all four forest types were enhanced with longer treatment time, and the effects for O-P and Ca-P were diminished by prolonged treatment. All the factors examined had significant interactions with forest type(P < 0.05). The transformation of inorganic phosphorus fractions in soil interacted with inorganic phosphorus forms, types of organic acids, the time of culture, acid concentration and forest type. 【Conclusion】The activation of soil phosphorus by organic acids was a slow and continuously dynamic process. Low-molecular-weight organic acids could affect the composition of inorganic phosphorus in the soil, and promote the dissolution of insoluble phosphate, thus improving the availability of soil phosphorus. This study showed that oxalic acid, citric acid and acetic acid affected soil inorganic phosphorus fractions in four different typical temperate forest types, and improved the availability of inorganic phosphorus fractions in the soil.