Objective To analyze the effect of ultra-pulsed carbon dioxide fractional laser therapy on scar improvement and skin physiological function in patients with depressed acne scars. Methods The clinical data of 70 patients with depressed acne scars treated in our hospital from January to December 2024 were retrospectively analyzed. According to different treatment methods, they were divided into the conventional group and the experimental group, with 35 patients in each group. The conventional group received conventional drug therapy, and the experimental group was treated with ultra-pulsed carbon dioxide fractional laser on the basis of the conventional group. The scar improvement, skin physiological function, treatment effect and adverse reaction rate were compared between the two groups. Results After treatment, the VSS score of the experimental group was lower than that of the conventional group (P <0.05). The skin elasticity and stratum corneum hydration in the experimental group were better than those in the conventional group (P <0.05). The total effective rate of the experimental group was higher than that of the conventional group, and the incidence of adverse reactions was lower than that of the conventional group (P <0.05). Conclusion The application of ultra-pulsed carbon dioxide fractional laser in treatment of depressed acne scars can facilitate scar repair, optimize patients’ skin physiological function, elevate the total treatment effective rate, and reduce the incidence of adverse reactions.