Due to the plains occurring in the mountainous space in Hilly-Gullied Loess Region during the process of urbanization, this paper takes the Southern New City of Yan’an as the research subject to explore the constitution mode under the ecological pattern. Based on the analysis of ecological elements of the region, integrating the construction requirements of regional ecological pattern and the adaptability of the mountain city, this paper proposes a series of strategies for urban construction and conservation of ecological patterns. It aims to construct the space constitution mode for mountain city adapting to the characteristics of the ecological pattern in the Hilly-Gullied Loess Region. It’s expected that it will provide references for space expansion of Hilly-Gullied Loess Region.