This paper defines the concept of spatial equilibrium of water resources firstly． That is，on the basis of ensuring the coordinated development among the three major subsystems of water resources，social economy and ecological environment in each computing unit，the coordinated development of different computing units is realized． Secondly，this paper introduces the concept of“coordinated development degree”into the study of the spatial equilibrium of water resources，and uses two levels of nested coordinated development as the metrics of spatial equilibrium． Based on the traditional water resource allocation model，this paper adds objective function and constraints of spatial equilibrium and then constructs the water resource allocation model based on spatial equilibrium． Finally，taking Yancheng City as an example，this paper constructs the water resource allocation model based on spatial equilibrium in Yancheng City and calculates the water resources allocation result under the 75% guarantee rate of 2020 in Yancheng City