Acne often leads to acne scar, which is the result of a variety of factors related to acne. It can be generally divided into two categories, one is atrophic scar, the other is hypertrophic scar and keloid. The existence of acne scars will seriously affect the external appearance of the human body, and even lead to psychosocial dysfunction. Its treatment is a major clinical difficulty. This article reviews the research progress on the mechanism of acne scar formation, in order to provide new ideas for clinical treatment of acne scars.