Abstract: The transport of air pollutants from cities in the north of China and neighboring countries is researched by using isentropic trajectory model. The trajectories are calculated twice daily for some larger cities in January, April, July and October for the period of 1992-1994. The statistical method has been used to deal with trajectory dots at intervals of 30 minutes for the forward and backward trajectories during 0-24h and 24-48h. The probability distribution diagrams of trajectory can show clearly the ensemble properties of isentropic trajectories for each city and the dominant transport directions of pollutants. Those possess no table seasonal variations. The forwar dtrajectory areas of China of the Ulaan Baatar in Mongolia can spread over north of China, and those of the Chita in Russia can spread over the northeast areas of China except summer. In July the forward trajectory of Pyongyang and Seoul can extend within the boundaries of China.