Abstract: This study investigates the cause and the dynamic structure on a small-scale snowstorm event occurred in the Shandong peninsula with the Doppler radar, profile, automatic station, routine sounding and surface observation data. the results are as follows: (1) Precipitation occurred in the two stages: the first weak precipitation one was typical snowstorm caused by the Huanghe cyclone with the characteristic of weak snowfall and north-east radar echo, and the second strong precipitation one behind the cyclone was ocean-effect snowstorm with the characteristic of strong snowfall and south-west radar echo.(2) Favorable synoptic situation led to the occurrence of the first stage snow, such as the obvious trough, cyclonic circulation, southwestern low-level jet and surface cyclone. Its vapor came from the South China Sea. The snowfall was distributed to ahead of southwestern low-level jet on the right and eastern side of the surface cyclone. (3) By contrast, the second precipitation stage occurred after the trough passed the Shandong peninsula and the cyclone passed through the Bohai straight to the Huanghai Sea. Cold air intruded into the Shandong peninsula from the Bohai straight and the Huanghai Sea. North-east wind was prevailing and its speed was stronger than the north-west wind, which brought rich water vapor and heat. Snowfall distributed within north-east wind. And,(4) the structure of wind field in the lower troposphere was different during the ocean-effect snowstorm. At the beginning, there was a mid-γ scale low circulation beside the north coastal area in the Shandong peninsula, and radar radial velocity shows a meso-β vortex in low level. Meanwhile, there was a shear between the south-east wind and north-west wind near the east coastal area. During the strong snowfall, a shear between the north-east and north-west wind was found in the boundary layer. Both the low circulation and shear are the favorable dynamic factors. As a result, the case implies that remarkable difference between the Bohai strait/Huanghai Sea and the Bohai Sea ocean-effect snowstorm, the former is behind the Huanghe cyclone, and the latter is common and typical, in terms of the wind field structure, motion of radar echo and precipitation distribution.