To explore the efficacy and safety of type A botulinum toxin combined with diprospan in the treatment of scar after thyroid surgery. Methods From May 2020 to May 2021, 60 patients with scar after thyroid surgery admitted to the Department of Plastic Surgery and Beauty, Changzhou Second People's Hospital Affiliated to Nanjing Medical University were randomly divided into control group and observation group, with 30 patients in each group. The control group was treated with diprospan injection, and the observation group was treated with type A botulinum toxin combined with diprospan injection. The clinical treatment, scar condition and adverse reactions were compared between the two groups. Results The clinical conditions of scar color, width and convexity in the observation group were better than those in the control group. The Vancouver scale score, scar width, scar assessment scale (PSAS) score and patient satisfaction score of the observation group were better than those of the control group (P <0.05). The incidence of adverse reactions in the observation group was 3.33%, which was lower than 20.00% in the control group (P <0.05). Conclusion Type A botulinum toxin combined with diprospan is more effective than diprospan alone in the treatment of scar after thyroid surgery, with higher safety and higher patient satisfaction, which is worthy of clinical application.