Based on conventional observations, data of intensified automatic weather stations, and NCEP reanalysis data, the meteorological characteristics of the sea fog maintenance and dissipation mechanisms during the 2018 Shanghai Cooperation Organization Qingdao Summit are analyzed. The results are as follows. 1) The visibility lower than 1 000 m corresponds to the relative humidity of 99% and the visibility between 1 000 m and 2 000 m corresponds to the relative humidity between 95% and 99%. 2) When southeasterly winds continuously blow near the surface over the Yellow Sea above 30°N and a water vapor convergence center is formed in Qingdao, it is favorable for the formation of sea fog in Qingdao. The sea fog tends to dissipate when southeasterly winds turn to northeasterly winds and the water vapor convergence center is weakened or disappears. 3) During the sea fog maintenance phase, the lowest inversion layer is stable below 980 hPa, the total temperature inversion difference gradually increases, and the sharply increasing of temperature inversion gradient synchronizes with the enhancement of the sea fog intensity. The sea fog is gradually weakened 12 hours after the decrease of the maximum and the total thickness of the inversion layers, and the visibility increases with the increase of the lowest inversion layer. 4) Sinking movement happens above the inversion layer and ascending movement below it in the daytime, while ascending movement happens below 700 hPa and the center of ascending movement is below the inversion layer in the nighttime. This vertical structure is favorable for the maintenance of the inversion layer and the sea fog. When the temperature inversion intensity decreases and vertical movement happens throughout the troposphere below 700 hPa, the sea fog tends to dissipate.