The millimeter wave radar was introduced into the Ningbo Beilun Port area in the late 2016, as a new technique of sea fog monitoring. Based on the visibility monitoring data of several regional automatic stations around Beilun Port from 2015 to 2018, the characteristics of sea fog distribution are summarized. Through the analysis and comparison of two lowvisibility weather cases in 2018, it is concluded that millimeter wave radar has obvious advantages in sea fog monitoring in port areas. The analysis shows that the fog days are different in different regions, the fog days monitored in coastal area are more than those in land, and also the fog days monitored in the high altitude areas were more than those in the lower altitude areas. The sea fogs in the harbor areas mainly appear in March to June and have the tendency of increasing month by month. In the case of sea fogs monitored by millimeter wave radar, the echo intensity is about -20 dBz, which can completely record the spatial distribution of fogs and their generation and elimination processes. The millimeter wave radar can clearly monitor the layered distribution of clouds and fogs.