Against the backdrop of a highly uncertain environment and high-quality transformative de-velopment,synergistically enhancing urban resilience and development efficiency while balancing secu-rity and development has become crucial for resource-based cities to achieve a sustainable and secure transition.Taking China's prefecture-level resource-based cities in China from 2009 to 2019 as the re-search object,this study constructs an evaluation index system for resilience and green development ef-ficiency,analyzes their coupling coordination relationship and spatiotemporal evolution characteristics,and identifies the key factors influencing their coupling coordination using a Tobit regression model.The results indicate that:1)the resilience level of resource-based cities has significantly improved,though the absolute level remains relatively low,presenting a gradient pattern of"regenerating>mature>growing>declining".Meanwhile,the green development efficiency exhibits a distinct"in-verted N-shaped"fluctuation,showing a distribution pattern of"growing>regenerating>mature>declining".2)The coupling coordination degree between the two systems has achieved an overall leap from"widespread incoordination"to"preliminary coordination"presenting a spatial pattern of"higher in the east than in the west,and stronger in the south than in the north".The resilience and green de-velopment efficiency combinations and urban life cycles exhibit significant structural differentiation.By the end of the study period,the"high resilience-low efficiency"combination accounted for the highest proportion,indicating that lagging green development efficiency has become the primary bottleneck re-stricting the system synergy of most resource-based cities.3)The proportion of the secondary industry and population size exert positive impacts on the coupling coordination relationship,whereas the eco-nomic growth rate and educational expenditure exert negative effects.Furthermore,the driving mecha-nisms exhibit heterogeneity across different types of resource-based cities.These findings can provide policy insights and decision-making references for promoting the secure and green transformative development of resource-based cities in the new development stage.