Xi Jinping's concept of 'lucid waters and lush mountains are gold and silver mountain of invaluable assets' (known as the 'Two Mountains' transformation) outlines a series of progressive development processes for achieving sustainable development in China. To assess the performance of regional ecological civilization construction, it is essential to establish a method for identifying the stage of the 'Two Mountains' transformation. In this study, a methodology was developed by using threshold identification and sliding t-test to identify the stages of the 'Two Mountains' transformation in three specific regions: Tangshan City, Nantong City, and Bama Yao Autonomous County. The results show that: 1) The tipping points, where the cost of resources and environment slows down relative to economic growth, serve as the core for identifying the transition from the stage of 'lush mountains in exchange for gold mountains' to 'valuing both lush mountains and gold mountains'. The peak inflection point further indicates the shift towards the stage of 'preferring lush mountains over gold mountains'. 2) As resources and environmental costs continue to decrease, the tipping points where the non-physical value of ecosystems becomes prominent, serve as the core for identifying the effectiveness of 'lush mountains are gold mountains'. 3) Different regions pursue distinct paths to realize the 'Two Mountains' transformation. Eastern regions have spearheaded a strategy involving treatment after pollution, whereas environmentally sound but economically disadvantaged western regions require impetus from national ecological compensation and collaboration with more advanced regions to achieve leapfrog development. The research shows that analyzing the evolving relationship between environment and economic is a valuable foundation to identifying the stage of regional 'Two mountains' transformation.