Based on the data of networked wind profiles and Doppler radars， ground automatic weather observation station， radiosonde and FY-4 satellite， combined with the ECMWF ERA5 1 h 0.25°×0.25° reanalysis data， this paper analyzes the spatial structure， formation， maintenance and function of PMDV that occurred in boundary layer to lower troposphere in North China during the blizzard weather on 14 February 2020.Besides， the moisture transported by multiple air flows and the net inflow are calculated and compared.The results indicate that PMDV was located in the front of the 500 hPa cold vortex， within the 850 hPa warm inverted trough and on the noutheast backflow.The PMDV was suspended vortex， with a horizontal range of 100~300 km and a vertical thickness of 1.2 km and a life span of 17 h.It first appeared in the boundary layer and then extended to higher altitudes（top at 2 km） and finally disappeared in the boundary layer.One of the reasons for formation of PMDV was that the strong and persistent east-northeast wind blew westward and then turned counterclockwise after being blocked by the Taihang Mountains running from northeast to northwest.Another reason was that the stronger frontogenesis appeared at PMDV primary position and it had maintained about 4 h ahead of complete cyclonic wind field circulation formed.The reason for maintenance of PMDV was under the common action of decompression （caused by warm advection）， weaker frontogenesis （caused by dense temperature gradient） and release of latent heat of internal condensation.The PMDV promoted the strengthening of low-level jet and the increase of positive vorticity in the southeast of its northeast side （blizzard area）， causing the upward movement， water vapor transport and aggregation in the study area to increase.Most moisture transported in the blizzard area was originated from multiple air currents below 850 hPa， among which the southeast branch contributed most， accounting for 86.4% of the total net inflow.The wet layer carried by the northeast branch airflow was concentrated in the 850 hPa layer， but the northwest airflow maintained dry all the time.Though the wet layer of southwest branch airflow was deep， the net inflow of water vapor above 700 hPa was very small.