[Objective] In order to reveal the characteristics of phosphorus composition in closed inland lake,and the influencing factors of endogenous release.[Methods] The phosphorus content in different medium of Dali-Nor Lake was determined. Using factor analysis to classify the factors affecting sediment release.[Results] The average value of total phosphorus (TP) in the water on Dali-Nor Lake was 2.00±0.02 mg/L, and the mean value of interstitial water TP was 2.50±0.02 mg/L. The sediment TP is between 206.09 to 940.49 mg/kg. Inorganic phosphorus (IP) in sediments accounts for 47.9% of TP, which is one of the main forms of phosphorus in sediments. Followed by iron-aluminum bound phosphorus (Fe/Al-P, 62.73±28.34 mg/kg) and exchangeable phosphorus (Ex-P, 36.50±19.13 mg/kg) By using the factor analysis method to analyze the influence of 13 sediments release indicators, there are 4 main factors, the 13 indexes are divided into 3 categories:TP, Ca-P, Fe/Al-P and bioavailability of phosphorus content in sediments classified as phosphorus in sediments and interstitial water factor; phosphorus concentrations of pH, DO, Eh of the water as the interface influence factor; The third is water depth to lakes characteristic factor.[Conclusion] There is a risk of release of sediment phosphorus sediment in Dali-Nor Lake. According to the results of factor analysis, the factors affecting sediment release are divided into three categories:sediment phosphorus, water-sediment interface physical and chemical indicators and lake water depth.