Combining the weather situation and the data of the upper level wind field, 370 m tower monitoring, ground elements, laser cloud height meter, and millimeter wave radar monitoring, the sea fog process on 15 February 2018 in the waterway of Ningbo Beilun Port is analyzed. The results show that this was a sea fog process dominated by the prefrontal fog. Under the background of the upper warm and lower cold front, the surface water vapor was abundant, the wind force was mild, and the structure of nearinverse temperature provided favorable conditions for the formation and maintenance of the sea fog. The upper and lower atmospheric wind directions were inconsistent, which was not conducive to the vertical air exchange, but conducive to the generation of fogs or hazes. The optical properties and process evolution trend of fog droplet particles can be clearly obtained by the backscattering coefficient, extinction coefficient and depolarization ratio monitored by the laser cloud altimeter. With the formation, development and dissipation of the sea fog, the intensity of the backscattering coefficient also became increased, intensified and gradually weakened. The droplet particles were small and light in fog weather, and the fluctuation amplitude was large. The Fourier transform frequency spectrum of particles at a certain height had a higher corresponding frequency, the proportion of which was more than 50%.