Taking China’s 31 provincial-level administrative regions, excluding Hongkong, Macao and Taiwan as research objects, this paper systematically evaluates the phased characteristics, regional disparities and dynamic evolution mechanisms of the regional-scale decoupling relationship in China from 2003 to 2023 by employing methods including remapping of decoupling index, kernel density estimation, Dagum Gini coefficient decomposition and spatial Markov chain. The results indicate that China’s overall decoupling level has improved steadily, among which eastern region has maintained a high-level decoupling state for a long time, and central and western regions present a pattern of coexisting phased improvement and structural fluctuation. Decoupling index shows an overall upward trend in each period with continuously enhanced regional coordination, but a certain degree of reversal has occurred from 2021 to 2023. Interregional disparity is dominant contributor to unbalanced decoupling development, and unbalanced regional development is core issue. Although the internal coordination of each region has gradually improved over time, polarization trend has intensified in the later period. Since 2021, provincial decoupling index has exhibited significant spatial agglomeration characteristics: eastern region has formed a high-high agglomeration area with high decoupling level, while some western provinces have formed a low-low agglomeration area with low decoupling level. The regional decoupling state presents obvious spatial dependence and neighborhood spillover effects. The high decoupling state of neighboring regions can significantly increase the probability of local upward transition, while the adverse state also poses the risk of spatial diffusion.