In this study the current status of the ambient air quality in the main cities of Pearl River Delta region was investigated. Two special administrative regions (Macau and Hong Kong) and three major cities of Guangdong (Guangzhou, Dongguan and Foshan (I resort the order to be consistent with the later parts)) were selected for analysis according to their geographical distribution, population, gross domestic product and industrial importance. The air quality of each city was diagnosed by using the monitoring data of 2014 and by applying the HYSPLIT model. This region is found affected by transboundary pollution outside the Pearl River Delta but the local emissions are the most important. The Asian Monsoon system also influences the air masses transport pattern.