Based on the collected activity data and emission factors, the Pearl River Delta (PRD) regional non-road mobile source emission inventory was developed by categories with the use of appropriate estimation methods for different non-road mobile sources. The results show that the total emissions of SO2, NOx,VOC, CO and PM10 from non-road mobile sources in the PRD region were about 6.52 x 10(4) t, 1.24 x 10(5) t, 4.54 x 10(3) t, 2.67 x 10(4) and 4.51 x 10(3) t, respectively. The marine source is the largest non-road mobile source contributor to SO2, NOx, CO and PM10 emissions, accounting for 96.4%, 73.8%, 39.4% and 50.5%, respectively; Freighter and dry bulk carrier are important marine emission contributors, sharing 89.8%, 81.8%, 77.3%, 79.5% and 81.7% of the total marine SO2, NOx, VOC, CO and PM10 emissions. The non-road mobile source has become the third largest SO2 and NOx contributor in the PRD region, accounting for about 8.6% and 13.5% of the regional total SO2 and NOx emissions.