Objective To observe the effect of collagen dressing adjuvant therapy on scar condition in facial acne depressed scar. Methods A total of 60 patients with facial acne depressed scar admitted to Wuxi No.2 Chinese Medicine Hospital from December 2023 to January 2025 were selected as the research subjects, and they were divided into the control group and the experimental group according to the random number table method, with 30 patients in each group. Both groups were treated with Er:YAG laser. The control group was additionally treated with chlortetracycline hydrochloride ointment, and the experimental group was additionally treated with collagen dressing adjuvant therapy. The scar condition, aesthetic effect, clinical efficacy and serum p38 MAPK pathway protein levels were compared between the two groups. Results The scores of VSS and ECCA in the experimental group after treatment were lower than those in the control group (P <0.05). The GAIS score in the experimental group after treatment was higher than that in the control group (P <0.05). The total effective rate of treatment in the experimental group (96.67%) was higher than that in the control group (76.67%) (P <0.05). The levels of ERK1, ERK2, MEK1 and MEK2 in the experimental group after treatment were lower than those in the control group (P <0.05). Conclusion The application of collagen dressing adjuvant therapy in facial acne depressed scar can improve facial scar condition and appearance, regulate serum p38 MAPK pathway protein levels, and enhance the treatment effect.