Parameters like aquifer depth, aquifer replenishment rate, aquifer medium, soil medium, percolation medium, and the coefficient of permeability are considered during the preparation of a groundwater vulnerability diagram. The analytic hierarchy process is used for evaluation, and expert scoring is used to analyze and establish the judgment matrix, and then new weights have been computed for each DRASTIC parameter, such that some subjectivity can be reduced to some extent and the weight value tends to be reasonable. Various spatially referenced digital data layers are overlaid to analyse with the partition diagram in GIS spatial analysis and a comprehensive simple and straight diagram is drawn. The study area is a plain of Naiman Banner, Inner Mongolia China, and covers an area of approximately 10,700km2. The areas of lower vulnerability are mainly located in the south. Slightly higher vulnerability areas are mainly located in the north, and the others have medium vulnerability.