The medial canthus is a half-moon shaped webbed crease of skin located obliquely or vertically in front of the medial canthus, and is a racial characteristic of the Mongolian race. There are dozens of surgical approaches to correcting the medial canthus, mainly Y-V and Z shaping, as well as the Mustarde method, which combines both principles. However, the surgical operation is relatively complex, with too many additional incisions and a certain degree of local scarring after surgery, or problems such as recurrence of redundancy and inadequate correction of redundancy to varying degrees. We use a modified “L” shaped lower eyelid lengthening incision to correct the canthus, which is simple to design and operate, with the incision parallel to the lid margin, short operating time, satisfactory treatment results, and inconspicuous postoperative scarring. The canthus is divided into four types: eyebrow canthus, lid canthus, lid plate canthus, and inverted canthus, depending on the height and shape of the canthus, with lid plate and lid canthus being the most common. It is characterized by the fact that the redundant skin obscures the normal shape of the inner canthus and part of the visual field, resulting in a visual effect of wide spacing between the inner canthus and a low nasal bridge, and is often accompanied by a single lid or “inner double”, which seriously affects the aesthetics of the eye. The most common clinical condition is congenital canthus. In 1932, Von-Ammon proposed that the canthus was caused by too little skin forming the horizontal crease of the eyelid, and that the soft haze of the soft horseshoe crab calcium was the result of the distress of the old dislikes of the old name of the school. The weevil is not due to excess or lack of skin. The method of deep tissue excision to correct canthus has been proposed by some scholars. In China, some scholars have suggested that the canthus is caused by the misalignment and misconfiguration of the orbicularis muscle of the upper and lower lids at the beginning of the medial canthal ligament, and is accompanied by thickening of the subcutaneous tissue. Wang R et al. dissected 9 cadavers and showed that the medial canthal ligament is basically located at the level of the medial corner of the eye, and the medial canthal ligament is divided into 3 branches, which together start from the medial aspect of the lid plate and travel medially. The levels were superficial to deep: skin, anterior branch of the medial canthal ligament, superior branch of the medial canthal ligament, lacrimal sac, and posterior branch of the medial canthal ligament, respectively. It is proposed that the main cause of the medial canthus is the misconfigured orbicularis oculi and the pulling of the fibers of the anterior branch of the medial canthal ligament. The design of the procedure is simple: the canthus is cut directly into two layers and some or all of the misaligned, misconfigured, and abnormally oriented orbicularis muscle is removed under direct vision. The procedure is designed to restore the ideal position and shape of the orbicularis oculi and the connective tissue fibers and anterior branch fibers of the medial canthal ligament, and to reduce the possibility of postoperative scar growth. The soft horseshoe crab can also be used to reduce the likelihood of postoperative scarring. The recession of the upper eyelid margin to the top of the soft horseshoe crab can sometimes result in a small “cat’s ear”, which can be trimmed slightly. In the newly formed lower canthus, this procedure is performed by making an extended incision directly from the medial canthus along the lower lid margin, separating the ACA’s lower triangular flap, trimming it flush with the lid margin, usually without removing the superfluous triangular flap, and closing it with 7-0 nylon sutures, thus avoiding an incision perpendicular to the lower lid margin and avoiding scar formation in the lower inner canthus. Thus, the modified “L” shaped lower lid lengthening incision not only corrects the medial canthus and shortens the medial canthus distance, but also ensures that there is no recurrence and no obvious scarring after surgery. Surgical points and precautions: ① Set point A: it is appropriate to reveal the tear mound well, usually 3-5 mm; too short a distance affects the tear mound reveal and also directly affects the length of the postoperative eye fissure; too long a distance, too close to the nasal side, is prone to scar formation; ② Set point A’: 2 mm from the inner corner of the eye, the skin edge of the inner canthus, in order to facilitate suturing and the establishment of a new inner canthus point, AA’ transverse incision in line with the principles of plastic surgery treatment; ③ Set C-point: the length of the C-point and the medial canthus depends on the relationship between the redundant skin and the lower lid margin, usually 8-10 mm, and the A’C incision is 2-3 mm from the lower lid margin. the incision is parallel to the lower lid skin line, and the prognostic scar is inconspicuous or absent; ④ AC A’lower triangular flap treatment: it is generally not necessary to perform a triangular flap excision because sometimes the redundant skin is nearly perpendicular to the lid margin, and in the “medial canthus type This is common in the “medial canthus” and “inverted” flaps, and scarring can be easily formed after excision of the triangular flap skin. The AC A’ triangular skin can be fully freed, or the C point can be properly extended along the lower lid margin, so that the skin can be redistributed to the lower lid margin and trimmed and sutured; ⑤ fully release and sever the misaligned, misconfigured and abnormal orbicularis muscle and the anterior branch of the medial canthal ligament to eliminate the cause of the medial canthus. The modified “L”-shaped lower eyelid lengthening incision method of canthus correction is simple in design and operation, the incision line is concealed, there are no multiple and small flap designs, incisions, and transposition sutures, etc. It is easy to grasp and apply, and it is suitable for all canthus, the near and long term scar is not obvious, the effect is ideal, and it is worth promoting. However, it should still be performed with caution for those with obvious scarring.