The fractional composition of sediment phosphorus was investigated in Lake Soyang. The fractionation was made in four major forms; loosely bound phosphorus on the surface of detrital particles, (Fe+Al) complexed phosphorus, organically bound phosphorus, and apatite phosphorus. The major forms of sediment phosphorus in Lake Soyang are organically bound (60.9%) and (Fe+Al) complexed (33.0%) phosphorus. The sediments are in high content of total organic carbon (1.40%) and in low C/N ratio (5.62). This presents the organic matters deposited in the surficial sediments in Lake Soyang are not mineralized well, so these organic rich sediments have a high pollution potential on the overlying water body.