With the construction of new district of small and medium-sized mountain cities in the western region of our county, it is the prerequisite to develop ecological spatial pattern for future development. This paper explains the concept of ecological urban design, which contains the features of eco-design with natural elements and low carbon design with artifi cial environment. And aiming at the existing problems in small and mid-sized mountain cities, it proposes the ecological urban design principles and strategies: keeping and remodeling the natural elements to achieve ecological compensation; building the blocks with small scale and mixed-use function which is fi t with the terrain conditions. Finally, it takes the urban design project of Qijiang new town as an example to elaborate the strategies specifi cally.