Rongcheng Swan Lake is a small lagoon in eastern Shandong Peninsula, China, whose water quality and ecological environment has deteriorated in recent years. The surface and core sediments were collected from Swan Lake to investigate the concentrations and spatial-vertical distribution of total phosphorus (TP) and various P forms. TP concentrations of the surface sediments (0-10 cm) were low, ranging from 79.15 mg kg-1 to 565.12 mg kg-1. TP concentrations in sediments were relatively high in the northwestern and central lake, and low near the sand spit, which was largely influenced by the anthropogenic inputs and sediment grain size. Inorganic P (IP) was the dominant form of TP, and apatite phosphorus (AP) was the major component of IP in surface sediments. At four of the six sediment profiles, the concentrations of TP, organic P (OP) and non-apatite inorganic phosphorus (NAIP) decreased rapidly with depth in the surface 0-10 cm layers, which was related to the increase of anthropogenic inputs in recent 20-30 years. In conclusion, the sediments in northwestern area had great potential for P release in the alkaline water of Swan Lake.