Abstract: This paper as studies the region take main urban area of Xi'an, based on geographic information system (GIS) and the cluster analysis, the fuzzy comprehensive judgment, has studied based on the GIS support urban geo environment quality comprehensive judgment method; According to main urban area of Xi'an geoenvironment characteristic, by considering such factor as terrain slope, engineering geological rock groups, structural type of rock and soil mass, ground water level, vegetation growth conditions, monthly precipitation, intensity of human engineering activities, uses Q cluster analysis to divides the district of survey into 25 geology environment quality district, divides into the whole city 25 geology environment quality district, and classifies them into 4 grades of geological environment quality by using fuzzy comprehensive judgment, it reflects the macro-distribution feature of the geological environment quality of main urban area of Xi'an objectively.