Surface sediments, columnar layer transect and interstitial water, collected in Gehu Lake during 1992~1993, are physically and chemically analysed, and phosphorus release of the sediments simulated in different conditions. The results show that within the depth of 0~20 cm each physicochemical index changed greater, but over 20 cm its difference was smaller. When the temperature being raised, oxygen concentration (or Eh) reduced, pH increased and hydrodynamic action exerted, the experimental systems were accelerated in the course of phosphorus release across the sediment-water interface, which wast however, restrained in the bacteria-free condition. The amounts of released phosphorus calculated by means of the results of laboratory imitation and model of concentration diffusion in interstitial water are, in the whole lake, 10.65t/a and 9.40 t/a respectively, of which the quantity of phosphorus released from the pen culture district makes up 28.2~35.4 percent. The internal phosphorus pollution of Gehu Lake will be controlled if the pea culture is strengthened in the management and its scale is properly cut down.