Objective To explore the effect of trephination combined with radiotherapy on serum collagen metabolism indicators in patients with thin keloid. Methods A total of 80 patients with thin keloid admitted to our hospital from March 2022 to December 2023 were selected as the research subjects, and they were divided into the control group (n =40) and the observation group (n =40) according to the random number table method. The control group was treated with trephination+hormone injection, and the observation group was treated with trephination+radiotherapy. The serum collagen metabolism indicators, clinical efficacy and the incidence of adverse events were compared between the two groups. Results The serum levels of Procollagen Ⅲ and COMP in the two groups at 3 months after operation were lower than those before operation, and those in the observation group were lower than those in the control group (P <0.05). The VSS score and recurrence rate in the observation group at 12 months after operation were lower than those in the control group (P <0.05). There was no significant difference in the incidence of adverse events between the two groups (P >0.05). Conclusion Trephination combined with radiotherapy can reduce the levels of serum Procollagen Ⅲ and COMP in patients with thin keloid, with better clinical efficacy and good safety.