Based on routine observational data, NCEP reanalysis data by every 6 hours and daily FY-2G satellite data, a heavy snow with freezing rain happened on 18-19 November 2020 in the southeast of Inner Mongolian is analyzed, including the circulation situation, water vapour condition, dynamic condition and stratification characteristics. The results show that: The atmospheric circulation anomaly was the main atmospheric circulation background of the disastrous weather; The westerly trough at 500 hPa, southwest jet at 700 hPa and northeast jet below 850 hPa, and the cyclone were mainly influencing systems, with the characteristics of a return-flow heavy snow. The water vapour transportation by the southerly and easterly and the moisture convergence provided sufficient water vapour supply, with the maximum specific humidity of 5 g·kg^-1 at 850 hPa and 4 g·kg^-1 at 700 hPa. The warm air represented by the southerly jet converged with the cold air of the north. The warm and humid air lifted on the low-level “cold pad”, which intensified the development of ascending motions and led to the rapid enhancement of precipitation. The diabatic heating had little effect on the frontogenesis, and the horizontal movement term primarily contributed to frontogenesis. The change of frontogenesis corresponded to the intensity of snow very well, so the front lifting force couldn’t be ignored in the increase of heavy snow; the maintenance of the frontal zone made the low temperature in the low level, and there was temperature inversion on the front. The warm and humid air rised along the front, and the “cold pad” below 900 hPa and “warm cover” above existed for a long time, which led to the occurrence and persistence of heavy snow. The temperature inversion on the front and melting level was conducive to the precipitation phase transformation. The temperature of the middle layer was higher than 0 ℃, and the upper and lower layer temperature was below 0 ℃, which corresponded to the stratification characteristic of melting freezing rain.