This paper focuses on the hot air and cold air processes of the float glass annealing lehr, and analyzes in detail the differences between them in terms of structure and technology. Structurally, the insulation zone of the cold air process annealing lehr has an inner and outer frame, while the hot air process has no inner frame, and they also have their own characteristics in terms of cotton filling methods and cooling duct selection. Technologically, there are differences in the flow direction of the cooling air, the cooling method in zone B, and the fan air volume. The hot air process uses a mixed hot air circulating counter-flow cooling method in zone B, while the cold air process uses a cold air counter-flow cooling method. Moreover, the hot air process consumes relatively more energy, but the cold air process has certain advantages in the production of ultra-thick glass. Through comprehensive analysis, it is concluded that there is no absolute superiority or inferiority between the two types of annealing lehrs. Glass manufacturers should choose the process according to their own operating habits. At the same time, the two processes can also learn from each other and make improvements to meet the development needs of the glass industry.