The fogging problem of glass viewports of optical devices significantly reduces the imaging quality, and its severity is closely related to the liquid film thickness. Through visualization experiments, the condensation process and growth state of droplets on the surface of inorganic glass with different contact angles were investigated, and the changing rule of the droplet condensation process of hydrophobic glass under different supercooling degrees and relative humidity was analyzed. It is found that the hydrophobic glass effectively slows down the droplet condensation in the early stage, while the hydrophilic glass forms a thin water film in the middle stage through droplet spreading, which interferes less with the imaging; the degree of subcooling and relative humidity are positively correlated with the rate of droplet condensation. Under the condition of high relative humidity of 92% RH, the condensation rate of droplets in the lower is 1.3 ~ 1.6 times that under the condition of low humidity of 72% RH; the coverage of condensed droplets on the hydrophobic inorganic glass tends to be stabilized, and then the peak value fluctuates between 45% and 60%; in the early stage of condensation, the thickness of the liquid film is positively proportional to the time of condensation, and a fitted linear equation between the two has been derived. These experimental results provide an important basis for the material selection and anti-fog design of equipment glass windows in specific environments in engineering practice.