Through remote sensing detection, it was found that from October to March of the following year, every 2 to 3 days, there was floating dust blowing from the westerly belt at an altitude of more than 2 kilometers. When it arrived over the North China Plain, due to the lowered terrain. After the wind speed drops, the floating dust will be mixed down with the pollutants, and the fine particles will rapidly increase after encountering water vapor, causing a large-scale high-intensity pollution phenomenon. If the south side is relatively strong, it will form a continuous multi-day Heavy polluted weather. This text is intended to explain the air pollution phenomenon in North China? ['Causes of Formation.', 'Formation process.', 'Coverage.', 'Time of occurrence.']