Using the ground observation data of Xuwen National Station from 1990 to 2023 and the NCEP/NCAR reanalysis data, the climate change characteristics, meteorological element characteristics and the common weather pattern of the occurrence of dense fog in the Qiongzhou Strait were statistically analyzed. The results show that: (1) The annual average number of foggy days in the Qiongzhou Strait is 166 days, the inter-annual change of foggy days fluctuates greatly, and the overall trend is decreasing, but it is not significant. Winter is the season with the highest frequency of dense fog in the Qiongzhou Strait, accounting for 51.8% of the total number of dense fog days in a year. The frequency of dense fog in the rest seasons (spring, autumn and summer) are 27.7%, 12.7% and 7.8%, respectively. February is the month with the most dense fog days in the Qiongzhou Strait, with an average of 4.2 foggy days, accounting for 2.3% of the total number of dense fog days in a year; followed by January and March, with an average of 3.0 foggy days each accounting for 18.1%, while July has the least average number of dense fog days, only 0.3 days. Dense fog in the Qiongzhou Strait mainly occurs in the morning from 4 to 8 a.m., accounting for 42.7% of the whole day, with a peak at a.m., followed by 7 a.m., and the least at 13 a.m. (2) The ideal meteorological conditions for the formation of dense in the Qiongzhou Strait are as follows: the surface wind is mainly easterly (ENE-ESE), with the wind speed concentrated in 1- m/s; the temperature is between 16-22℃; the temperature dew point difference (T-Td) does not exceed 2.0℃ the station pressure is between 1005-1017.5 hPa; the relative humidity is higher than 90%. (3) The circulation patterns of fog in the Qiongzhou Strait can be divided into five categories: the front low-pressure, the high pressure entering the sea, the stationary front, the front of cold front, and the equal pressure field, with the proportion 10.8%, 13.5%, 21.6%, 24.3%, 29.8%, respectively. Among them, the front low-pressure type and the high pressure entering the sea type mainly produce advective fog, the stationary front type often produces mixed fog, the front of cold front type produces frontal fog, and the equal pressure field type mainly produces radiation fog. The five types of weather patterns and the fog types they generate provide significant reference value for practical operations.