The aim is to eliminate the permanent stress and structural imbalance in the glass products. Glass is a poor conductor of heat, molding, surface and inner temperature difference in the cooling process, the surface solidification shape, inner viscous shape, and stress relaxation does not exist on the surface temperature difference, the temperature difference of cooling to room temperature, the inner surface is temperature shrinkage, hinder the generation Zhang Yingli, while making the surface compressive stress, permanent existence. The size and distribution of the permanent stress caused by the thermal process are not uniform in all parts of the product. Therefore, it will affect the strength of glass products, or even self stress due to the stress concentration. Annealing can eliminate the harmful tension inside the glass and prevent the new stress from producing. During annealing, the glass product is heated or heated to maintain the annealing temperature. The original stress is relaxed and eliminated, and then slowly cooled below the strain temperature. After the glass enters the rigid body completely, the temperature difference between the inner and outer layer only generates temporary stress. Because some properties and function of glass (such as optical glass, glass thermometer) in the transition temperature range, great viscosity structure of the particle moving slowly, resulting in the performance and no time to reach equilibrium temperature, use will have performance changes due to slow balance therefore must maintain enough time in the annealing temperature.