Trajectory clustering analysis and potential source contribution function (PSCF) analysis are applied for the characteristics of air pollutant transport in China’s BeijingTianjinHebei Region during winter months, and the construction of transport index is improved. On this basis, a heavy air pollution process is used to investigate the effect of transport index. The results show that the probabilities of heavy pollution weather with air masses coming from south, west, east and northwest direction are descending for Beijing, Tianjin and Shijiazhuang. In the surface level, the enhancement of southwesterly and southeasterly wind becomes the main path of air pollutants to Beijing in most time, and the southeastern source of pollutants are mainly concentrated in the lower atmosphere. The improved transport index has a better ability to describe the relationships between air pollutant transports and local PM2.5 concentration. The interregional transport has an obvious influence on the PM2.5 concentration in Beijing, Tianjin and Shijiazhuang, and shortdistant transport from suburbs and surrounding areas has the most significant impact. Therefore, a reasonable application of transport index is useful in making a preliminary judgment on the causes of heavily polluted weather.