The variations and difference of the formal nitrogen and phosphorus exchanges across the sediment-water interface in Tsuchiura Bay and the central part of Lake Kasumigaura were studied under a laboratorial control of aerobic and anaerobic conditions, the results show that in aerobic, the released NO₃^--N, NO₂^--N, NH₄⁺-N and PO₄^3--P observed are smaller than in anaerobic. And the exchanged DTN and DTP were in fluctuation states, the net release nearing to zero. In anaerobic. an obvious release occurred for the most of nutrients, the release rates of NH₄⁺-N and PO₄^3--P were 2-8 times as much as in aerobic. By a comparison between the sediment samples in the corresponding nutrient concentrations and their release rates, a conclusion is drawn that the nutrient content ratio, at the vSediment-water interface, namely the differenciation between the intervStitial and the superficial lake water, was a decisive factor of the release rate in quantity.