The Yangtze River Economic Belt Development Strategy, committed to environmental conservation and sustainable development, not only enhances the Belt"s development quality but also significantly impacts its eco-efficiency.Taking the implementation of the Yangtze River Economic Belt development strategy as a quasi-natural experiment,this paper uses the super efficiency SBM model to analyse the spatial and temporal evolution of the eco-efficiency and the double-difference method to assess the impact of the development strategy of the Yangtze River Economic Belt on the ecological efficiency along the route. The results of the study found that: 1) From 2007 to 2021, the eco-efficiency of 11 provinces and municipalities in the Yangtze River Economic Belt showed a gradual upward trend, with a gradual rank leap in the low-value areas, an increasing number of high-value areas, and a significant phenomenon of spatial clustering of eco-efficiency. 2) After the policy point, the growth rate of eco-efficiency in 11 provinces and municipalities accelerates significantly, especially in the middle and lower reaches, and the eco-efficiency value shows a significant increase across the levels. 3) The differences within the Yangtze River Economic Belt gradually increase, forming a development pattern of downstream, midstream and upstream areas in decreasing order, which is mainly determined by inter-regional and intra-regional differences. 4) The policy evaluation model shows that the development strategy of the Yangtze River Economic Belt significantly improves the eco-efficiency of the provinces and municipalities along the route, and the conclusion passes the robustness test and the placebo test. 5) Economic growth, innovations in science and technology, government intervention and industrial structure have a significant contributing role in enhancing the ecological and economic efficiency of the Yangtze River Economic Belt, and the speed of the enhancement of eco-efficiency in each province is positively correlated with the level of economic development. Yet, the impact of the Yangtze River Economic Belt Development Strategy on the eco-efficiency on each province is polarised, and the synchronicity of the development of eco-efficiency in each province is weak.