The forms of phosphorus (P) in sediments is an important factor affecting the exchange between sediment and water interface. A fourstep extraction method was used to analyze various P forms in sediments of Baihe zone in Miyun Reservoir. The results indicated that total P ranged from 505.11 to 829.56 mg·kg^-1. The concentrations of various phosphorus forms were ranked in order of HCl-P > BD-P > NaOH-P > NH₄Cl-P. HCl-P and BD-P were the main forms of P in the sediments, together accounting for 53%-80% of TP concentration. Spatially, TP concentrations were generally higher from the deep sites and the transitional zone between Baihe zone and Chaohe zone. This pattern may be attributed to the small grain size of the sediments. According to the difference of TP concentration in the interstitial water and overlying water, inflow site (Taoli) and transitional zone (Kubei) were the sources of the internal P loading. Other sites were the sinks of internal P loading. This phenomenon may be determined by the temperature and dissolved oxygen of the overlying water together. The concentrations of various P forms in sediments were decreased from 2002 to 2013, indicating that the comprehensive measures of water environment management in the upstream of Miyun watershed were in effect.