Abstract: The paper aims to reveal the causes of heavy snow weather, and provide reference for forecasting and early warning of agricultural disastrous weather. Based on conventional observation data and NCEP reanalysis data, the authors diagnosed and analyzed synoptic situation and physical conditions of a heavy snow process from November 23 to 24, 2015 in northwestern Shandong. The results showed that: the main effect system of the heavy snow included the westerly trough, the low-level jet and the cold high pressure on ground, and the heavy snow had characteristics of the backflow of snow; the main feature was warm moist air above boundary layer climbing along the cold air layer; the main reason for the snowfall distribution was that specific humidity under the boundary layer in the south was more than that in the north; during the heavy snow process, there were strong updraft and warm advection above 925 hPa, and weak downdraft and cold advection in boundary layer.