1. From the morphological point of view, the difference between a single eyelid and a double eyelid is that the skin of the whole upper eyelid is thick and appears bloated, and the skin droops slightly, covering the eyelid margin, and the root of eyelashes is invisible when looking up; The skin of the upper eyelid is thin and delicate, and the skin of the upper eyelid is not drooping, and the eyelid margin is all visible. The eyelid fissure of single eyelid is short and narrow; The eyelid fissure of double eyelid is longer and wider.

2. Differences in anatomical structure: Because the occurrence of single and double eyelids is influenced by race, region, heredity, age and other factors, there are significant differences in morphology, so there are also obvious differences in anatomical structure. The skin of single eyelid is thicker, the subcutaneous tissue is higher, the orbicularis oculi muscle is more developed, and there is more fat behind the orbicularis oculi muscle; The tarsal plate of single eyelid is thin and narrow, and the levator palpebralis muscle, which opens eyes, is underdeveloped; The double eyelid person is just the opposite.