This paper constructed a spatial equilibrium evaluation model of water resources combined with the relationship between supply side and demand side. Based on the quantitative evaluation and analysis of the state and change process of water resources spatial equilibrium level by the five-element connection number, the evaluation model of water resources spatial equilibrium is constructed, and the evaluation system of water resources spatial equilibrium including 12 evaluation indicators of the supply subsystem and the demand subsystem is established. Then, the development trend and influencing factors leading to the change of water resources spatial equilibrium level are diagnosed and analyzed by the subtraction set pairs. Applying the model to 11 counties and districts in Ulanqab City, the study shows that the spatial balance level of water resources has been improved from 2011 to 2020 in 6 counties and 5 counties, among which Jining District has been in a low level of equilibrium. From 2011 to 2020, the overall level of spatial balance of water resources in Ulanqab City has shown a trend of improvement year by year. In the level of supply subsystem in 2020, Jining District is in a counter trend state, while Huade County and Shangdu County are in a counter trend state. At the demand subsystem level, only Jining District is in a negative state. The vulnerability indicators of Ulanqab City are water resources per capita and water demand load of ecological environment.