Abstract: The development and utilization of geothermal resources is of help to adjust the energy structure, to improve environmental quality and to reduce pollution. The geothermal water in Xi'an sag of Guanzhong Basin has good occurrence conditions and abundant resources for large-scale development and utilization.Few research has been conducted yet on the division and the amount of the geothermal resources in Xi'an sag. In this paper, the geothermal reservoirs in Xi'an sag are divided into four types:Honghe Bailuyuan Formation, lengshuigou koujiacun Formation, Lantian Bahe Formation and Zhangjiapo Formation. The authors systematically analyzes the reservoir cap characteristics, formation lithology and sedimentary equality of each type. Through the chemical analysis of geothermal water, it is considered that in the vertical direction, the geothermal water storage environment is more closed in the deeper part while in plane,the environment is relatively closed in the middle part.In the south and the north,the chemical environment is relatively open. Combined with the regional geo-temperature data, the paper calculates the depth of the constant temperature layer of the proluvial plain and the alluvial plain, and analyzes the characteristics of the geotemperature field and the regional geotemperature gradient at the depth of 20m, 500m, 1500m and 2000m. Using the volume method, this paper evaluates the total volume reserves, total elastic reserves and total static reserves of geothermal water in Xi'an sag.The total volume reserves are 5270.96×10⁸m³, total elastic reserves are 16.89×10⁸m³ and total static reserves are 5287.85×10⁸m³. On the basis of the studies of geothermal water resources in Xi'an sag, the authors hold that the area is rich in geothermal water resources. The stability of the thermal reservoirs makes it relatively safe for development and utilization. Development and utilization of geothermal water in the area is of significance to control pollution and reduce haze, to adjust energy consumption structure, and to improve people's livelihood as well.