Domestic and international scholars have paid considerable attention to research on intercity co-opetition relationships. Based on the systematic examination and analysis of previous research results, the article, starting with the theory of the ecological niche, regards the modern city as special life system with ecosophy from the perspective of phytocoenology. Cities in certain regions may have various relationships. Co-opetition between cities usually plays an essential role in whether the cities can achieve continuous development together in the same city group. The percentage of a particular city's resource occupation in its group is reflected by its comprehensive development level, the utilisation of resources is represented by the niche breadth, and the co-opetition of 20 cities in county areas of the Hexi Corridor is clarified by cluster analysis and the structural division of the eco-system. Finally, a realistic strategy for co-opetition is put forward by virtue of the ecological niche, aiming to provide theoretical suggestions for coordinated and continuous development in city groups of the Hexi Corridor. It is concluded that all the cities in the region have made mixed progress in terms of their comprehensive development levels, with their ecological niches experiencing mixed ups and downs. The positive correlation observed between a city's comprehensive development level and its ecological niche width shows that the occupation and utilisation of resources are two supplementary coefficients. Among the 20 county-level cities in the region, Jiayuguan and Jin Chuan District have always been categorised as Tier I, as they always top the list of cities with highest ecological niche; Liang Zhou District, Su Zhou District and Gan Zhou District are Tier Ⅱ cities; Akesai, Yumen, Dun Huang and Su Bei are Tier Ⅲ; and the remaining 11 cities are Tier IV. Based on the analysis of the eco-system structure in the cities of the Hexi Corridor, together with theories such as niche dislocation, expansion, coordinated development, the following corresponding co-opetition strategies are proposed:Jiayuguan District and Jinchuan District need to play a radiating and exemplary role, with coordinated development in the Liangzhou District, Suzhou District and Ganzhou District. This activity will drive other cities' development, reaching a balance for the ecology niche in the city system of the Hexi Corridor.