Based on the precipitable water vapor received from the ground based GPS and ground automatic stations, as well as weather data, a return flow snowfall in Hebei province is studied. The results show that: (1)GPS precipitable water vapor increased from southwest to northeast before the snow, corresponding to the warm and humid southwesterly flow, and decreased from north to south after the snow because of the clod high. (2) The main effect system was the high level trough in the first stage; GPS precipitable water vapor showed increasing trend, and the actual precipitation increased first and reduced then; the main effect system was the return flow in the second stage, and the actual precipitation occurred at the peak of GPS precipitable water vapor or during the decreasing phase. When the cold high moved from north to south, GPS precipitable water vapor decreased, and the actual precipitation weakened and stopped. (3) In the sounding stratification of the return flow snowfall, the high humidity layers were near the ground and the 700 hPa layer, and the low humidity layer was between the high humidity levels.