The increase of PM_(2.5) concentration has a vital influence on atmospheric visibility, human health and climate change. This paper adopts the monitoring data of the Yangtze River Delta in 2015, employs the analytical method of exploratory spatial data and relative coefficient method, and analyzes the spatial-temporal pattern and influencing factors of PM_(2.5) in cities of the Yangtze River Delta. The results showed that: 1) The average annual concentration of PM_(2.5) in Yangtze River Delta region is 54.54 mug/m~3. The level is high in spring & winter and low in summer & autumn in general. January and December are the months of most polluted, with widest range of pollution. The concentration is low in months during May to September. The average daily value of wave period in spring and winter is shorter and intense, while in summer and autumn is longer and gentle. 2) In 2015, the average annual concentration of PM_(2.5) in the Yangtze River Delta region is decreasing from Jiangsu to Zhejiang, which has the characteristics of high in north and low in south, local projecting. 3) In the Yangtze River Delta region, low concentration of PM_(2.5) in the urban agglomeration is mainly distributed in the coastal area of Zhejiang Province, and the high value agglomeration is mainly distributed in the South of Jiangsu area. 4) The soot emitted by burning and the quadratic transformations of precursor has a significant impact on the concentration of PM_(2.5) in Yangtze River Delta region. Wind speed and precipitation are the two important meteorological factors that affect the concentration of PM_(2.5).