| Water fluctuation zone refer to strip of convergence zones between land and water which are submerged and outcropped periodically because of seasonal fluctuation of Rivers, lakes and reservoirs. After construction of three gorges project,it will regulate water level of Three-Gorge Reservoir through the method of accumulating clear water and discharging mixing water, and form water fluctuation zone,the total area of which are over 348.93 Km2 and the fall is about 30m.As a strip of convergence zones between land and water, its ecosystem is sensitive and fragile, so its effect on reservoir water quality, especially on reservoir eutrophication is a problem deserved attentions. When being submerged, soils in water fluctuation zone will make material exchange with overlying water through a series of biochemical action, and release nutrients such as nitrogen and phosphorus to waters in suitable conditions, supplying the growth requirements of phytoplankton. Therefore, research about release potential and release mechanism of Water fluctuation zone soils in Three-Gorge Reservoir is an important link to control and governance reservoir eutrophication. So in this paper, the author selects 100 soil samples in Water fluctuation zone and 25 sediments in submerged area from 5 tributaries of Yangtze River in core zones of reservoirs, from the analysis of soil physical and chemical properties and phosphorus forms, making conclusions as follows:In research areas, the variation range of total soil nitrogen in water fluctuation zone was 0.459～2.735mg/g,and its mean was 1.317±0.483mg/g,while the total nitrogen of sediments in submerged area was in 1.003~1.917 mg/g,and its mean was 1.368±0.174 mg/g.The difference of soil total nitrogen among different basins is obvious, in that the total nitrogen in Zhu Yi basin and Da Ning basin is highest, far higher than mean in research areas and other basins. Total nitrogen in Ru Xi basin takes second place and Tang Xi basin is lowest. The difference of total nitrogen of sediments in among different basins is also obvious, in that the total nitrogen in XiaoJiang basin and Ru Xi basin is higher, while total nitrogen in Zhu Yi basin and Da Ning basin is lower. Difference of Soil total nitrogen of water fluctuation zone from different ground utilization manners was also obvious, the total soil nitrogen content in water fluctuation zone from infield and garden plot or holt was obviously higher than those from badlands. In research areas, the variation range of total soil phosphorus in water fluctuation zone was 0.314～2.799mg/g,and its mean was 0.676±0.282mg/g,while the total phosphorus of sediments in submerged area was in 0.484～0.987 mg/g,and its mean was 0.703±0.246 mg/g. The difference of soil total phosphorus among different basins is not obvious, in that the total phosphorus in Zhu Yi basin and Da Ning basin is slight higher, total phosphorus in Xiao Jiang basin takes second place and Tang Xi basin is lowest. The difference of total phosphorus of sediments among different basins is obvious, in that the total phosphorus in Ru Xi basin is highest, while total nitrogen in Zhu Yi basin and Da Ning takes second place and Xiao Jiang is lowest. Difference of Soil total phosphorus of water fluctuation zone from different ground utilization manners was not obvious.In selected samples, the variation range of Fe/Al-P is 0.013～0.101 mg/g,and its proportion is 3.73%～20.63%,while the variation range of Ca-P is 0.019～0.203 mg/g,and its proportion is 5.8%～35.39%,and OP taking the proportion of TP 37.3%～89.81%,which is in leading position of all phosphorus forms. The correlation between TP and all other phosphorus forms have reached extremely significant level, in which the correlation between OP and TP is best, while correlation between Fe/Al-P and TP is worst. It means that TP is mainly determined by OP and Ca-P. The correlations between different phosphorus forms also reach significant level, but its correlation coefficient is low.Compared with some urban lakes, soil total nitrogen and total phosphorus in water fluctuation zone in Three-Gorge Reservoir is lower, but compared with natural lakes, soil total nitrogen and total phosphorus in water fluctuation zone in Three-Gorge Reservoir is in a high level. In selected samples, the rate of phosphorus which can be used by microorganism,in that (Fe/Al-P+OP)/TP reach to 57.9%～94.2%,and its mean is 74.0%.Compared with some fleet lakes in middle and nether reaches of the Yangtze River, it is in a high level, therefore in research areas the upper limit rate of phosphorus of soils in reservoirs which can be used by microorganism is higher. If external conditions is suitable, its release potential to overlying water is great.
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