Evaluation and Influencing Factors of Regional Environmental Efficiency in China Based on Three-Stage <i>DEA</i> Model

China needs high-quality economic development while environmental problems are intensifying. The deteriorating resource and environmental situation have caused serious hindrances to economic and social development. Therefore, we decided to explore the primary causes of environmental pollution and resource waste and provide efficient solutions for future ecological management and environmental optimization. Our study is based on panel data of inter-provincial regions in China from 2011 to 2020 and uses a three-stage [Formula: see text] model to evaluate the level of environmental efficiency, the trend of change and its variability among regions under the same environment, which accurately and objectively reflects the true level of environmental efficiency of each region in China. The results found that: (1) The adjusted environmental efficiency levels of the inter-provincial regions in China change significantly. (2) Without the influence of external environmental factors and random error factors, the real environmental efficiency among provinces in China is significantly unbalanced. (3) There is a significant influence of external environmental variables on the actual environmental efficiency. Therefore, to further improve the level of environmental efficiency in China, it is imperative to encourage a wider range of market accessibility; optimize the industrial structure; learn from excellent development experiences; reasonably increase capital investment in environmental management; and improve the environmental awareness of enterprises.