This paper aims to introduce the new constraints of PM2.5 into the environmental efficiency research framework, based on the provincial panel data of China during 2001-12. The authors examine environmental efficiency with and without consideration of PM2.5, conduct hypothesis tests on these environmental efficiencies, and analyze the energy savings and haze reduction. The results indicate that the overall environmental efficiency score is inefficient. The average environmental efficiency scores are 0.706 and 0.867 with and without the consideration of PM2.5, respectively, and omitting PM2.5 would result in biased environmental efficiency change. In addition, empirical analysis shows that there is an unbalanced regional development and significant differences among provinces in environmental efficiency. Last but not the least, the potential savings of energy, water, and regional haze reduction average 24.26%, 39.16%, and 26.49%, respectively.