A large-scale continuous heavy fog weather occurred in the central and eastern regions of China, including North China, Huanghuai Region, the middle and lower reaches of the Yangtze River, and South China during 3-6 January 2017. The low visibility below 70 m in Jinan lasted for more than 6 h and the minimum visibility was only 51 m. Based on the data from fog droplet collector and automatic weather station, the microphysical structure of the fog was analyzed, the main characteristics of fog in four “development-weakening” subprocesses were discussed, the evolution characters in different development and burst reinforcement phases of the fog were studied, and the causes of the dense fog and burst reinforcement were also discussed in this paper.