Based on the systematic synthesis of previous studies, main aquifers in inland catchments in northwestern China were summarized, groundwater circulation in mountains, plains and deserts were described, and groundwater flow systems in plains were specifically analyzed. Due to the tight connection between groundwater and surface water, aquifers and rivers are hydraulically connected to form a system. Therefore, either groundwater or surface water exploitation in the upper stream can result in significant changes in water resources in the entire catchment. Groundwater resources assessment shows that the total groundwater resources are 78.3 billion m³/a, of which it is 48.7 billion m³/a in plains, 19.9 billion m³/a in mountainous areas and plains, and the current mining rate is 12.8 billion m³/a. Groundwater resource potential analysis indicates that groundwater potential is limited except the Cadam basin and the southern marginal areas of the Tarim basin. Hence, groundwater carrying capacity can only be increased by enhancing groundwater utilization efficiency. In the further, saline or brackish water utilization, research on underground water reservoirs, studies on groundwater ecological function and ecological water requirements should be enhanced to provide technical support for the rational development of water resources.