Abstract: Groundwater has been polluted in different degree all over our country which poses considerable influence for economy. Groundwater vulnerability assessment can give directions on water planning and management. Based on the groundwater vulnerability assessment approaches used all over the world, this paper has established fuzzy synthesis approach using DRASTIC model in Nanchang city. The new approach overcomes difference of DRASTIC rating and discontinuousness on index value. It tries to seek optimization of DRASTIC rating and continuous change on parameters. The concept of index standard eigenvalue has been cited in order to determine index rating. Considering the data and information obtained in the study area, index standard eigenvalue matrix which sets corresponding to 10 linguistic classes used for determining the groundwater contamination degree of every parameter has been founded and relative optimization value has been established. This new approach is applied to groundwater vulnerability assessment in programming area with MAPGIS software, The result shows that the distributing pattern of contamination are well consistent with groundwater environment quality forecasted and measured in this area., which has practical meaning in helping relative departments to establish prevention project and management steps of groundwater contamination.