Phosphorus is one of the important nutrient elements in the forest ecosystem and a limiting factor for plant growth in arid and semi-arid regions. However, after the sandy grassland is transformed into an artificial forest ecosystem, how the growth of artificial forests affects the changes of sandy soil phosphorus is still unclear, which brings uncertainty to the rational management of artificial forests on sandy land. This study chose 20 samples of Pinus sylvestris var. mongolica sand-fixing forests at different growth stages (including young forest, middle-age forest, mature forest and over-mature forest) in Zhanggutai area of Liaoning Province (with 4 adjacent natural grasslands as controls) as objects, sampled and measured the soil chemical factor values--soil phosphorus (total phosphorus and available phosphorus), soil nitrogen (total nitrogen and available nitrogen), soil potassium (total potassium and available potassium), soil organic carbon, pH value etc. and the soil physical properties--soil moisture content, soil particle size distribution, soil bulk density etc. of the 0-10, 10-20, 20-40, 40-60, 60-80, and 80-100 cm layer of the sample plot, and performed statistical analysis. The results show that: after plantation of P. sylvestris var. mongolica plantation on sandy grassland, the content of soil total phosphorus gradually increases with the stand age, and reaches the highest level in mature period. However, total phosphorus is not sensitive to soil depth. The soil available phosphorus content in mature period is higher than that in the young and middle-age period. The available phosphorus content in over-mature period is the lowest, but shows few significant differences with young and middle-age forests. In addition to, after the grassland is planted with P. sylvestris var. mongolica forest, the total phosphorus is also mainly affected by soil bulk density and soil available nitrogen, and the available phosphorus is mainly affected by soil organic carbon and pH value. In summary, after planting P. sylvestris var. mongolica plantation on sandy grassland, stand growth has promoted the increase of the soil total phosphorus content, while has a slight decrease of the soil available phosphorus content. The survival and growth of the over-mature P. sylvestris var. mongolica forest has led to the excessive consumption of the soil available phosphorus, making the content of soil available phosphorus lower than that of the grassland. Attentions should be paid to this aspect to ensure the rational management and healthy development of P. sylvestris var. mongolica plantation.