Since 2013, the annual average mass concentration of PM2.5 in Beijing’s urban area has been decreasing year by year, but heavy PM2.5 pollution incidents have continued to occur frequently, and there are still many uncertainties in the causes and physical and chemical mechanisms of the rapid or even explosive growth of pollution. This study analyzes the thresholds of conventional meteorological elements, PM2.5 and its chemical components under three growth mechanisms of slow, rapid and explosive growth, as well as the correlation between the changes in meteorological elements and the increase in pollutant concentration from 2013 to 2020 in Beijing urban area. The results showed that from 2013 to 2020, the average accumulation rate of PM2.5 showed a trend of slowing down, and the proportion of slow growth in the accumulation phase of PM2.5 increased year by year in Beijing. Under the premise that the criterion is gradually strict, the proportion of explosive growth has not changed much year by year (4%—7%).The PM2.5 concentration threshold for an explosive increase from 2013 to 2016 was 62 μg m-3, and after 2017, the threshold was strict to 45 μg m-3. 82 μg m-3 is the threshold value that is extremely prone to explosive growth of PM2.5 since 2018. After this value, the probability of explosive growth will increase significantly. Organic aerosol (Org) played a vital role in the explosive growth. In the same time interval, the contribution of Org to the growth concentration of submicron aerosol species (PM1) is slow growth < fast growth < explosive growth, and the contribution of primary OA (POA) in rapid and burst growth to Org growth concentration on average exceeds 50%, which is higher than the average proportion of 40% during the study period. Among the inorganic components, the contribution of SO42? in increasing concentration of PM1 shows explosive growth (13%) > fast growth (11.8%) > slow growth (11.1%), while the contribution of NO3? is opposite. The contribution of secondary particulate matters (SPM) in the cumulative phase is higher than that of primary particulate matters (PPM), but in the explosive growth, the contribution of PPM to the pollution increase (up to 45%) is significantly higher than 33% in the average period, indicating that the contribution of PPM to the explosive growth cannot be underestimated. After the explosive growth began, the temperature decreased (0.2-1.2°C), while the humidity and pressure increased significantly in autumn and winter. The main air mass in the explosive growth is southward (the three heights account for 69%-82%), followed by the eastward direction (12%-20%) in Beijing urban area.