Abstract: The benthic fluxes of PO4-P at the sediment-water interface in fish cage area of Dapengao were measured by laboratory incubation experiments, and a function method with dependence of the exchange rate was developed. In the function method, the average exchange rates of PO4-P at the sediment-water interface were calculated. The results show that: (1) the relation between PO4-P exchange fluxes and incubation time fit the e exponent attenuation function; (2) the exchange rates of PO4-Pat the sediment-water interface varied from 0.27 to 2.47 mmolm-2d-1 in the whole area, but the exchange rates varied from 0.82 to 2.47 mmolm-2d-1 in the fish cage area, were obviously higher than those in the control area varied from 0.27 to 0.62 mmolm-2d-1. Since phosphor were accumulated gradually in the long period breeding process, the exchange rates of PO4-P in the fish cage area increased accordingly.