Abstract: According to the analysis of the main problems in DRASTIC model,which is used for assessing groundwater vulnerability,the groundwater vulnerability is regarded as a fuzzy and stochastic concept.A modified groundwater vulnerability assessment model was developed,which based on fuzzy theory and an improved AHP method. The modified model and DRASTIC model were both applied to assess the aquifer vulnerability in Dongguan Town.The results derived from the two methods are similar in the whole,but the grade changing of the modified model is more sensitive and the distribution is more precise,which shows the spacial continuous of aquifer vulnerability.So it is consistent with the practical situation and easy to use.