Abstract: Qingyang City is located in a hillygully region in the central Loess Plateau, it is arid, and the ecological environment is fragile. In this paper, the spatial structure evolution of urban system in the study area was analyzed based on the ecological carrying capacity. The results showed that there was a traffic directivity in the study area during the period of 1985-2010, and the town development was restricted by the limited traffic conditions. Urban distribution was related to the distribution of water resources, and it was different from different counties. Double center pattern was gradually formed under the optimization of urban system. The ecological elastic degree, carrying capacity of resources and load pressure strength were used in the evaluation. The results showed that the ecological elastic degree and carrying capacity of resources in the study area were holistically in an ascendant trend during the period of 1985-2010. Spatial structure of the regional urban system and the ecological carrying capacity interacted, and the relationship between the ecological carrying capacity and the spatial structure of urban system was discussed. Some measures were proposed for optimizing the spatial structure of urban system in the study area based on the ecological carrying capacity in such fragile ecological environment.

Key words: ecological carrying capacity, urban system, spatial structure, Qingyang city, Loess Plateau