Several typical sections of some embankment were studied by the method of environmental isotopes in the paper. The leakage sources of groundwater were ascertained. The result showed that the groundwater of No.1 borehole at Jiangdu dockyard, No.23 borehole at Xiaocaitan section and No.29 borehole at Lianmengzhuang dock was recharged by river water, the water of Heiyutang pond near No.5 borehole was recharged by the local precipitation or groundwater forming by recent precipitation, and the groundwater of No.7 borehole at Wanshougong section was the mixture of river water and local precipitation. Then the analysis of fuzzy clustering was performed by applying fuzzy clustering method that environmental isotopes and hydrochemistry values were taken as index characteristic values and endued different weights. The quantitative analysis result was in agreement with the conclusion qualitatively judged by environmental isotopes and hydrochemistry.