Objective To analyze the effect of carbon dioxide fractional laser combined with medical cold compress patch on skin physiological function and scar improvement in patients with acne scar. Methods A total of 78 patients with acne scar admitted to our hospital from June 2021 to June 2024 were selected as the research subjects, and they were divided into the control group and the study group according to the random number table method, with 39 patients in each group. The control group was treated with CO2 fractional laser, and the study group was combined with medical cold compress patch on the basis of the control group. The clinical efficacy, recovery time, skin physiological function, scar improvement and adverse reactions were compared between the two groups. Results The total effective rate of treatment in the study group (94.87%) was higher than that in the control group (76.92%) (P<0.05). The incrustation time, decrustation time, pain time and complete healing time in the study group were shorter than those in the control group (P <0.05). The stratum corneum water content of the study group at 3 months after treatment was higher than that of the control group, and the TEWL was lower than that of the control group (P <0.05). The scores of ECCA and VSS in the study group at 3 months after treatment were lower than those in the control group (P <0.05). There was no significant difference in the incidence of adverse reactions between the two groups (P >0.05). Conclusion CO2 fractional laser combined with medical cold compress patch in the treatment of acne scar can improve the physiological function of skin, improve the clinical effect, shorten the recovery time, and does not increase the incidence of adverse reactions, which can effectively enhance scar improvement.