We often see many children wearing glasses with one eye covered. This is doing amblyopia masking treatment. Amblyopia is a common disease that damages children’s vision during the sensitive period of visual development due to abnormalities in the internal and external visual environment, resulting in insufficient effective stimulation of visual cells at all levels, resulting in lower corrected distance vision in one or both eyes than normal children of the same age, and accompanied by abnormal monocular function in both eyes, with a final corrected visual acuity of less than 0.8. It is a common disease that damages children’s vision, and its prevalence has been reported to be 1.6%-3.6% in recent years. The prevalence of amblyopia has been reported to be 1.6-3.6% in recent years. Even due to the limitations, many preschool children cannot have vision examinations in time or the examinations are inaccurate, so it is difficult to detect amblyopia in one or both eyes, thus missing the best age for treating amblyopia in children. Among the conventional treatments for amblyopia, masking therapy is the most important and cost-effective method that has been used for the longest time, and its effectiveness has been proven by numerous studies and clinical practice. Masking therapy is mainly used for children with strabismus, refractive error, and amblyopia with a difference in visual acuity of more than 2 lines between the eyes. By temporarily suppressing the dominant eye (healthy eye, dominant eye, or dominant eye) and giving the amblyopic eye the opportunity to use it with appropriate benign visual stimulation, the masking reduces or eliminates the long-standing inhibition of the amblyopic eye by the dominant eye, allowing it to become excited again, thereby improving visual acuity. By masking, it also helps to adjust and establish normal retinal correspondence in both eyes, gradually restoring monocular function in both eyes. It is generally accepted that the younger the child is at the start of treatment, the faster the response to treatment and the better the prognosis. In children with strabismic amblyopia, 90% of those treated with full masking at 28-33 months of age have improved visual acuity, while the percentage of patients who improve when the same treatment is started at 12 years of age is almost zero. According to statistics, the best time to treat amblyopia is under the age of 7 years. In the process of treatment, the visual acuity of the amblyopic eye should be checked, and the visual acuity of the dominant eye should be checked to prevent vision loss due to masking. With the application of new technology and better understanding, the masking therapy has been improved and developed in recent years. In addition to the masking therapy, together with other amblyopia training, children can hope to get rid of the trouble of wearing glasses.