Abstract: Purpose/Significance Population and economic agglomeration are power of high quality development in China. Since the ecological environment is an important part of high quality development, how to coordinate agglomeration and environment is the key to realize sustainable development. Design/Methodology Based on the extended out density function, and China’s 289 prefecture-level cities panel data from 1998 to 2018, combing with spatial economics theory, from first tier cities, second-third-fourth tier cities, fifth tier cities, perspective to test how population and economic agglomeration affect haze pollution. Conclusions/Findings There is an N shaped cure relationship between population agglomeration, economic agglomeration and haze pollution. It shows that the promotion of urbanization and industrialization first increase haze pollution then decrease, when it exceeds the carrying capacity of land, environment and resources will aggravate haze pollution. Furthermore, the relationship between population agglomeration, economic agglomeration and haze pollution in medium-sized cities presents an inverted U shaped cure, but the agglomeration and haze pollution in Mega cities presents positively. The robustness test results further verify the above conclusions. Based on this, when leveraging the effect of scale economy to promote high quality development, environmental carrying capacity should be paid attention to, and controling haze pollution should adapt to regional joint goverance.