Objective: To investigate the clinical efficacy and safety of ultra-pulsed carbon dioxide laser combined with compound acid in the treatment of atrophic acne scars. Methods: Total 75 patients with atrophic acne scars were included in our research and randomly divided into two groups(A and B group)．Group A was treated by ultra-pulsed carbon dioxide laser combined with compound acid. Ultra-pulsed carbon dioxide laser was performed for 3 times, once every five weeks, the compound acid was used between the treatment. Group B was treated by ultra-pulsed carbon dioxide laser combined with alpha hydroxy acid. Follow-up was conducted for 3 months after treatment to evaluate the efficacy and adverse reactions．Results: A total of 73 patients completed treatment and follow-up. The total effective rates of group A and group B were 91.9％ and 83.3％, respectively, with no significant difference (x2=1.24，P＞0.05). The improvement of acne scar scores between the two groups before and after treatment showed no significant difference（t=1.57，P＞0.05）. Group A has an outstanding effect on V-type scars (t=2.07，P<0.05), however, both of groups have no significant effect on W-type scars (t=0.30，P>0.05) and U-type scars (t=0.02，P>0.05). The treatment satisfaction of group A was 97.30%, higher than group B（x2=4.01，P<0.05）. The incidence of adverse reactions in group A was 8.11%, which was lower than that in group B (x2=4.82,P<0.05). Conclusion: Ultra-pulsed carbon dioxide laser combined with compound acid is effective in the treatment of atrophic acne scars, which can improve the patient satisfaction rates, worthy of clinical promotion.