In the face of global warming, energy depletion, and air pollution, controlling greenhouse gas and air pollutant emissions has become an urgent task for an emerging economy. Therefore, this study investigates the synergistic relationship between haze decoupling and carbon emission decoupling in China, one representative emerging economy. Effect of synergistic decoupling is explored by decomposition model. Based on Geographically and Temporally Weighted Regression, this study also investigates spatiotemporal variation of the synergistic relationship between the two decoupling indices and the synergy effect of various factors. The main results are as follows. (1) Technological progress in CO2 is the main negative driving factor, and the ratio of potential CO2 to potential haze (potential ratio) is the main positive driving factor in the synergistic decoupling. (2) There is a synergy effect between two decoupling indices, and in the later period, the value of synergy effects tends to be flat. (3) The emission factor has the largest synergy effect. In the short term, the synergy effect of the population is greater than the energy intensity, but in the long run, the synergy effect of the energy intensity is greater than the population. These novel findings not only contribute to advancing the existing literature on synergistic emission reduction of environmental pollutions, but also merit particular attention from policy makers in the emerging economy.