In order to study the effects of phosphorus application level on phosphorus content of various forms and phosphorus balance of black soil after continuous straw return under corn and soybean rotation system，this study was conducted in Daxijiang Farm Co.，LTD.，Jiusan Branch，Beidahuang Group，in 2022 and 2023. In 2022，four phosphorus application levels of P2O5 0 kg/hm²(P0)，50.2 kg/hm²(P1)，71.8 kg/hm²(P2)and 86.1 kg/hm²(P3)were set up. In 2023，three phosphorus application levels of P2O5 0 kg/hm²(P0)，50.2 kg/hm²(P1)and 71.8 kg/hm²(P2)were set up，in which P2 treatment was the recommended local phosphorus fertilizer dosage. Soil samples from 0-20 cm soil layer were collected to determine the content of available phosphorus and phosphatase activity in soil. Hedley phosphorus fractionation method was used to determine the content of different phosphorus fractions in soil，and the correlation between different phosphorus fractions was analyzed. The results show that，on the basis of continuously returning straw to the field for 6 to 7 years，phosphorus fertilization significantly increased the soil available phosphorus content at each growth stage of soybean，but the difference between most phosphorus fertilization treatments was not significant. The contents of H2O-P，NaHCO3-Po and NaOH-Pi in soil treated with phosphorus fertilizer were significantly higher than those without phosphorus fertilizer，increasing by 41.75%-53.45%，23.07%-43.95% and 14.38%-33.38%，respectively. In 2022，the NaHCO3-Pi content of soil treated with P1，P2 and P3 was significantly increased by 17.06%，28.61% and 24.78%，respectively，compared with that treated with P0. In 2022，the HCl-P content of P2 and P3 treatment was significantly increased by 12.41% and 11.32% compared with P0 treatment，respectively. There were no significant differences in NaOH-Po and Residual-P contents among different treatments at two years. The correlation coefficients between NaOH-Pi and soil total phosphorus reached 0.954 and 0.940 in 2022 and 2023，respectively，and the correlation coefficients between H2O-P and NaHCO3-Pi and available phosphorus reached 0.945 and 0.987 in 2022，respectively，and the correlation coefficients between H2O-P and available phosphorus reached 0.951 in 2023. Soil acid phosphatase activity and alkaline phosphatase activity were decreased continuously with the increase of phosphorus application level，and soil acid phosphatase activity changed the most. Under the condition of straw returning to field，with the increase of phosphorus application level，the phosphorus carried out in grain increased first and then decreased. In 2022 and 2023，the phosphorus carried out in grain under P1 treatment was the highest，reaching 21.24 and 17.52 kg/hm²，respectively. The apparent balance of soil phosphorus in all treatments showed surplus in 2 years，and the apparent balance of soil phosphorus increased with the increase of phosphorus application level. In summary，after 6 to 7 years of continuous straw returning to the field in the black soil area，reducing the amount of phosphorus fertilizer by 30% in production could effectively balance soil phosphorus while maintaining a high soil available phosphorus level，and promote the efficient and safe utilization of phosphorus.