Phosphorus fractions, organic matter and particle size of the surface sediment from Chaohu Lake were analyzed for spatial distribution and the risk of phosphorus release. The result showed that total phosphorus (TP) of surface sediment was 790 mg x kg(-1), which was 55% higher than that in 1980s, with 386 mg x kg(-1) higher in western lake and 211 mg x kg(-1) higher in eastern lake. NaOH-Pi of sediment ranged from 55 to 648 mg x kg(-1), and occupied average 25% of TP. NaOH-Po of sediment ranged from 27 to 468 mg x kg(-1), and occupied average 17% of TP. NaOH-Pi and NaOH-Po in western lake were 331 mg x kg(-1) and 225 mg x kg(-1), which were significantly higher than those in eastern lake. Ca-P and Res-P accounted for 18% and 40% of TP, and were equably distributed in the lake. TP, NaOH-Pi and NaOH-Po of sediment in the western lake increased intensively with the depth, while Ca-P and Res-P showed no significant change in the vertical profile in the lake. Profile of phosphorus fractions showed that NaOH-Pi and NaOH-Po were the dominant factions of the increasing phosphorus sedimentation in the western lake. Phosphorus of sediment in the western lake will release more easily to the water with higher organic matter and higher content of sandy silt.