High-resolution pore water equilibrators (HR-Peeper) and diffusive gradients in the thin films ( DGT) technologies were combined to in situ measure soluble reactive phosphorus (c(PW)) and labile phosphorus (C(DGT)) on seven sites in the west of Lake Chaohu. Vertical distributions of c(PW) and c(DGT) in most sediment profiles were similar to a different extent, demonstrating that the buffer capacity of the sediment solids to pore water SRP was similar at different depths. The diffusion flux across the sediment-water interface (SWI) and the ratio of cDGT/ c(PW) (R) were used to characterize phosphorus activity in sediments. From the center of the lake to the estuary of Nanfei River, the values of c(PW) and c(DGT) within the 6 mm layer were below the SWI and the SWI diffusion flux gradually increased, reflecting an increase in pollution level of sediment phosphorus. The change of R values was unconspicuous, indicating that the buffering capacity of the interface sediment had no significant difference.