The Beijing-Tianjin-Hebei region is one of the most air-polluted areas in the world where PM_2.5 has been identified as the major air pollutant that has become the most restrictive factor in regional development. The study of PM_2.5 in cities and surrounding areas on a large regional scale (e.g., national scale) usually directly compares concentration differences and evaluates the impact of urban PM_2.5 pollution on the surrounding areas simply and quantitatively. This method of assessment of cities and surrounding areas is difficult to apply to small areas to quantify and analyze differences in pollutant direction and distances. Based on the data of PM_2.5 concentrations and land cover types of 13 cities in Beijing, Tianjin, and Hebei Provinces in 2000, 2005, 2010, and 2015, the average distance from the city center to the urban border was used as the basic distance reference, first- (one-time basic distance) and second-level (two-times basic distance) buffer analyses were performed for each urban area, which was then divided into eight quadrants to quantitatively analyze the impact of urban PM_2.5 pollution on the surrounding area to determine differences in pollutant direction and distance. The results are as follows: (1) the spatial-temporal distribution of air quality in all prefecture-level cities and surrounding areas in Beijing, Tianjin, and Hebei in 2000-2015 was divided into the following modes: first, high concentrations in urban areas and low concentrations in the surrounding areas; second, low concentrations in urban areas, high concentrations in surrounding areas, and the difference of concentrations is small; (2) the impact and scope of the surrounding cities on the surrounding areas is increasing, and is manifested in two aspects: distance and direction:① the farther the majority of the cities are from the urban area, the greater the potential impact of cities on the surrounding areas; ② in 2000-2015, except for Tianjin, Langfang, Hengshui, and Cangzhou, the other cities had significant differences in the directional characteristics of air pollution. In this study, a quantitative method was established to analyze the impact of urban PM_2.5 pollution on the surrounding area in Beijing, Tianjin, and Hebei Provinces, and expand the methodology for studying the impact of urban air pollution on the air quality in the surrounding areas. Research on environmental effects provides methodological and empirical methods to quantitatively analyze urban ecology.