The coupled and coordinated development of new urbanization and ecological environment holds significant importance for China’s sustainable and high-quality economic and social development. By constructing an index system for new urbanization and ecological environment, and utilizing a coupled coordination degree model, the coupled coordination degrees of new urbanization and ecological environment were calculated for 31 provinces and municipalities in China. Subsequently, the spatio-temporal evolution characteristics and driving factors of the coupled coordination levels between the two systems were analyzed using non-parametric kernel density estimation and geographic detector models. The results indicate the following: (1) The overall coupled coordination degree of the two systems in the country transformed from a mildly imbalanced state to a barely coordinated state. The coupled coordination degrees of the two systems exhibit a “east-central-west” descending distribution pattern across the three major regions, with distinct temporal and internal differences. (2) The overall, eastern, and central regions show a decreasing trend in the improvement rate and imbalance level of the coupled coordination, while the western region exhibits an increasing trend in both improvement rate and imbalance level. The phenomenon of regional divergence between the eastern and western regions is evident. (3) Economic development, social security, technological innovation, industrial structure, market environment, government capacity, and openness to the outside world have significant influences on the coupled coordination of the two systems. The interaction among factors is stronger than the individual effects of each factor, highlighting the need to pay more attention to the cumulative effects of multiple factors on the coupled and coordinated development of the two systems.