中文摘要：

选取福建省地下流体3个测点的水位资料，以提取M2波幅度为例，根据所选取采样数据长度的不同分别对提取出的M2波幅度进行比较。结果表明，M2波幅度随农历时间的变化而改变，在小潮时几乎接近于零，且不同长度的采样数据的对比证明，以月尺度数据求出的M2波幅度最佳。

英文摘要：

Three measuring points of the underground fluid level information are selected in Fujian Province. Taking the M2 wave amplitude extracting as a example, according to the selected sample data of different lengths, the M2 wave amplitude extracted are compared. It shows that M2 wave amplitude changes with lunar time. In a small tide, the M2 wave amplitude is almost close to zero. After the different lengths of sampling data for comparison, the M2 wave amplitude exacted from month scale is best.