Observations of Pearl River Delta (PRD) regional air quality monitoring network during 2006-2012 were employed to capture the temporal and spatial variation characteristic of air pollution over PRD and then the causes of that were analyzed. Air quality had improved generally in PRD region as result of the decrease in SO_2, NO_2 and PM_(10) concentrations by 61.7%, 17.4% and 24.3% during 2006-2012, though 12.5% increase in O_3 concentration in the same period. Air quality was better in wet season (April to September) than dry season (October to March), and the monthly-averaged concentrations of various pollutions were all bimodal, with peaks in December and March for SO_2, NO_2 and PM_(10) and October and May for O_3. The high concentrations for SO_2, NO_2 and PM_(10) were mainly distributed in Foshan and Guangzhou but for O_3 mainly in outside suburbs of PRD. The trends of concentration for different pollutants were not consistent in different regions of PRD. The central region of PRD had more significant decrease in primary pollutants, and those decreases were induced by many factors, especially in economic downturn and environmental protection policies. However, the relatively weaker control ofVOCs, as well as climatic change, could intensify the secondary pollution particular in O_3.