Soil organic phosphorus (P_o) is an important phosphorus pool in soils. The forms, contents and bioavailability of P_o change significantly with pedogenesis, which affects soil P supply, nutrient balance and ecosystem productivity. However, compared with inorganic phosphorus (P_i), previous studies paid less attention to P_o, which was mainly attributed to the difficulty in the extraction, analysis and identification of different P_o speciation. In recent years, the solution ³¹P nuclear magnetic resonance (³¹P NMR) spectroscopy was increasingly applied in pedology for characterizing P_o compounds, providing a new way for quantitative analysis of P_o forms and contents. This significantly improved our understanding of the transformation process of P_o during long-term terrestrial ecosystem evolution. This paper systematically summarized the forms and properties of soil P_o, and described the principle and procedures of solution ³¹P NMR spectroscopy for characterizing soil P_ospeciation. Then we reviewed the evolution trends and controls of different P_ospeciation during natural pedogenesis, and put forward several questions that need to be resolved in the future. Future research priorities include (i) determining the rates, pathways and thresholds of soil P_o transformation during long-term soil evolution; (ii) elucidating the coupling relationship between P_o and other nutrients such as C and N at different stages of soil evolution and the mechanisms of fixation and release of soil P_o; and (iii) building a quantitative model of P_o evolution in different types of soils. Providing solutions to the above questions can improve our understanding of the phosphorus biogeochemical cycle in Earth’s Critical Zone and provide a theoretical basis for nutrient management and regulation at different stages of soil evolution, and would promote sustainable utilization of soil resources.