Abstract:The natural conditions in the arid area of northwest China are very bad, precipitation is scarce, evaporation is intense, and water resources are scarce. In the meantime, natural lakes and wetlands, natural vegetation oases and soil salinization are strongly dependent on the ecological water level of groundwater. So that, it is an important task to construct the evaluation index system of groundwater ecological function in northwest arid area. Based on the study of the relationship between different types of ecological conditions and groundwater table depth in arid area, the evaluation index system of groundwater ecological function in arid area of northwest is constructed, which takes the shallow groundwater as the core factor. It is composed of 3 attribute indexes and its subordinate, the 3 attribute indexes include the maintenance of natural wetland landscape by groundwater, the maintenance of natural vegetation oasis, the maintenance of farmland land quality and. The application results in the middle and lower reaches of the Shiyang River Basin show that the index system is suitable for the evaluation of groundwater function in the arid and semi-arid areas of northwest China, and it also indicates that the ecological function of groundwater in the middle and lower reaches of the Shiyang River Basin is fragile, the weak and weak ecological function accounts for 87.86% of the total area of the demonstration application area, while the strong and strong ecological function of groundwater accounts for only 5.07%. Therefore, it is urgent to improve the ability of groundwater ecological function protection in arid area of northwest China.