To enhance our understanding of the distribution and transport of air pollution in the Yangtze River Delta (YRD) region, cruise measurements were carried out in the YRD. We focused on winter haze pollution and spring photochemical pollution over 2016~2018. It was showed that the PM_2.5 concentrations in the Yangtze River Delta ranged between 60 and 122μg/m³, varying largely with location. In the Wuxi-Changzhou area in the east of YRD, the Wuhu-Hefei area in the west, the Bengbu-Chuzhou area in the north, and the Huzhou-Hangzhou area in the south, the PM_2.5 concentrations were 20%~40% higher than other regions. The concentrations of O₃ were 9~52μg/m³ with unnoticeable spatial variation. The concentrations of ozone in Suzhou, Yancheng, Xuancheng and Wuhu were relatively high. We further used the FLEXPART_WRF model combined with the PM_2.5 emission inventory to explore the possible sources of PM_2.5 in the YRD. We found that Nantong and Shanghai were the potential sources of PM_2.5 when east wind prevails, while Lianyungang and Yancheng contributed more when north wind prevails. We simulated forward trajectories using FLEXPART for a pollution episode. We found the correlation coefficient between the cruise observations and the simulation reaches 0.9. Overall, there still existed regional PM_2.5 and O₃ pollution in YRD region, and cruise observation combined with the trajectory analysis is an effective tool to trace the regional transport of these pollutants.