Objective To analyze the effect of levorotatory vitamin C combined with Q-switched laser in the treatment of patients with pigmentation after acne. Methods From February 2020 to May 2024, 90 patients with pigmentation after acne who were treated in the Department of Cosmetic Dermatology of Shanghai CellCare Cosmetic Medical Co., Ltd. and the Department of Cosmetic Dermatology of Chenqiao Hospital were selected, and they were divided into control and observation groups by the random number table method, with 45 patients in each group. The control group was treated with Q-switched laser, and the observation group was treated with levorotatory vitamin C combined with Q-switched laser. The clinical efficacy, disease symptoms (pigmentation area and pigmentation color), appearance condition [melanin index (MI), erythema index (EI)] and skin condition were compared between the two groups. Results The total effective rate of treatment in the observation group was 95.56%, which was higher than 82.22% in the control group (P <0.05). After treatment, the scores of pigmentation area, pigmentation color, MI and EI in the observation group were lower than those in the control group, and the skin pH value and stratum corneum hydration were higher than those in the control group (P <0.05). Conclusion Levorotatory vitamin C combined with Q-switched laser is effective in the treatment of pigmentation after acne. It can effectively improve the pigmentation area, pigmentation color and skin barrier function, reduce water loss and increase stratum corneum hydration.