The heavy snowfall event in the southeast of Liaoning on 25 February 2015 is analyzed by using conventional observation data, NCEP reanalysis data, and Doppler radar data. The results are as follows. The heavy snowfall event occurs in the warm moist area on the east of the low-level shear line, which corresponds to the divergence area on the left of the outflow area of the upper-level jet stream, and there is a strong water vapor convergence center; under the uplifting effect of mountains, the surface southerly airflow introduces the wind direction convergence and jet stream center below 850 hPa in the heavy precipitation area, which is one of the main causes of the heavy snowfall. Six hours before the snowstorm process, the temperature advection decreases with height and the frontal zone is formed on the field of pseudo-equivalent potential temperature, which contributes to the development of vertically unstable stratification; 8-12 hours before the process, the development of the positive vorticity advection, wind direction convergence zone in the middle and lower level, and near-surface cold air layer and the formation of the secondary circulation strengthen the ascending motion, and these conditions are useful indicators for forecasting the heavy snowfall. The maximum radar echo intensity reaches between 40 dBZ and 45 dBZ when the precipitation phase shows rain or sleet, while the echo intensity is between 20 dBZ and 25 dBZ during heavy snowfall phase. When the temperature at 850 hPa and the thickness between 1 000 hPa and 850 hPa reach the conversion thresholds between rain and snow at Dalian station, rain or sleet appears in the north of Dalian, snow appears in the north, and the heavy snowfall occurs at this time. During the heavy snowfall, the echo height is basically below 6 km, the maximum echo intensity between 25 dBZ and 35 dBZ maintains below 1 km, the weak northerly winds prevail near surface layer, together with the southwesterly winds above, the shear layer is formed at the boundary layer, which lifts the wam moist air and provides dynamic conditions for the heavy precipitation.