Abstract: Air pollution caused by fog and haze is one of the key issues concerning  people’s livelihood and environment, which has plagued China’s economic development. In this research, the spatial pattern and influence factors of smog on air pollution in the Yangtze River Delta from 2015 to 2017 was empirically analyzed based on the improved output density model, statistical and spatial econometric models. The study found that: (1) Smog pollution possessed the characteristic of seasonal variation  in the Yangtze River Delta and the situation of air quality in the cities of this region has gradually improved. (2) Smog pollution had the characteristics of significant local agglomeration and spatial heterogeneity. Hangzhou, Ningbo, and Taizhou presented the feature of low-level agglomeration, and Chuzhou, Yangzhou, Zhenjiang and Taizhou were high-level agglomeration. The polluted area has been concentrated at the provincial boundary, and the level of contamination has been  gradually decreased from northwest to southeast. There was a significant intercity spatial positive correlation and spatial spillover effect of smog pollution, and the smog pollution in the surrounding areas has had a negative impact on this region. (3) The population concentration, R&D investment, industrial structure, industrial smoke and dust emissions and urban construction in the Yangtze River Delta have had positive impacts on smog pollution, while the factors such as the opening-up, energy consumption and precipitation have had a negative impact on smog pollution. There was no Kuznets curve relationship between smog pollution and economic growth. By optimizing the spatial distribution and combination of production factors, and sharing pollution control infrastructure, etc., economic agglomeration could have  an inhibitory effect on smog pollution.