Water space is where water cycles operate and circulate, it plays a critical role in the supply of water resources, regulation of local climate, control of flood and waterlogging, as well as the maintenance of ecosystem balance and diversity. It is crucial to the coordinate development of “economic society-ecological environment” combined system. In this paper, we put forward the concept and connotation of water space carrying capacity from the spatial perspective of water resources carrying capacity, and summarized the supporting roles of water space carrying capacity in the “economic society-ecological environment” system from two aspects of the spatial composition and spatial structure of the water space. With the consideration of discipline development and practical requirements of integrated water space management, the future research directions were pointed out as follows: water space carrying capacity evaluation system should be built based on the study of the linkage effects of the spatial composition and the spatial structure of water space carrying capacity; a coupled method of quantifying water space carrying capacity should be optimized and constructed; the research on water space carrying capacity of multiple spatiotemporal dimensions should be strengthened, so as to provide practical management and decision-making recommendations for the sustainable development and utilization of water space resources, as well as improve the carrying capacity of water resources in an all-round way.