Objective To explore the effect of subcutaneous separation with small needle knife combined with fractional CO2 laser on skin condition in patients with depressed acne scar. Methods A total of 62 patients with depressed acne scar admitted to our hospital from November 2024 to April 2025 were selected. According to different treatment plans, they were divided into the control group and the observation group, with 31 patients in each group. The control group was treated with fractional CO2 laser, and the observation group was treated with subcutaneous separation with small needle knife combined with fractional CO2 laser. The clinical efffcacy, skin condition, repair factor levels and complications were compared between the two groups. Results The total effective rate of the observation group was 93.55%, which was higher than 74.19% of the control group (P<0.05). After treatment, the scores of texture, pigmented spots, porphyrin and pores in the observation group were all lower than those in the control group, while the levels of EGF and bFGF were all higher than those in the control group (P<0.05). There was no statistically signiffcant difference in the incidence of complications between the two groups (P>0.05). Conclusion For patients with depressed acne scar, the combined treatment of subcutaneous separation with small needle knife and fractional CO2 laser has a deffnite treatment effect. It can effectively improve skin condition, promote skin repair, and has high treatment safety, which is worthy of clinical application.