In this paper, we used the panel smooth transition model (PSTR) to study the nonlinear relationship between sulfur dioxide emissions and economic growth in the three regions of China’s eastern, middle and western regions, based on panel data from 31 provinces and autonomous regions in China from 2005 to 2017. And calculated the elasticity of the impact of total export-import volume and urbanization rate on emissions. The empirical results indicate that economic development and sulfur dioxide emissions are positively correlated in the three regions of East, Middle and West. In the eastern region, when the economic scale is lower than the threshold value, it has a negative impact on SO2 emissions; but when it is higher than the threshold value, it has a positive impact on SO2 emissions, and the smoothing rate between the two regime is slow. The per capita GDP in the middle and western regions is weakly positively correlated with SO2 emissions. When the economic scale reaches the threshold value, its positive impact on SO2 emissions will increase, and economic development will further increase emissions.