中文摘要：

根据三沙湾多年实测潮位资料和2个临时潮位站的实测资料，分析了三沙湾潮汐特征，计算了纳潮量、海水的平均交换率和海水半更换期．结果表明：三沙湾潮差较大，有较强的纳潮能力．但由于其水域面积较大，地形也比较复杂，其整个区域海水的平均“更新能力”一般,当潮差累积率为20％（大潮）时，三沙湾的海水半更换期约为36个潮周期；当潮差累积率为50％（中潮）时，海水半更换期约为75个潮周期；当潮差累积率为80％（小潮）时，海水半更换期达到114个潮周期．

英文摘要：

Based on the measured data of two temporary tide stations and tidal data of many years of the Sansha Bay, the tidal characteristics of the Sansha Bay were analyzed, and the tidal prism, the average exchange rate and the half-exchange period of sea water were calculated. The result shows that the Sansha Bay is of high capacity in receiving tidal water, and that it has wide tidal ranges but low capacity of sea water exchange due to wide water areas and the complex landform, the half-exchange period of sea water of the Sansha Bay being about 36 tidal periods, 75 tidal periods, and 114 tidal periods as the accumulation rate of tidal ranges reaches 20% （spring tide）, 50% （moderate tide）, and 80% （neap tide）, respectively.