Objective To explore the clinical efficacy and safety of heated needle combined with ALA photodynamic therapy on moderate to severe acne. Methods Thirty patients with moderate to severe acne who were treated in our hospital from March 2022 to March 2023 were randomly divided into control group and observation group, with 15 patients in each group. The control group was treated with conventional drugs, and the observation group was treated with fire needle combined with ALA photodynamic therapy on the basis of the control group. The skin lesion reduction rate, clinical efficacy, skin aesthetics, skin lesion score, adverse reactions and complications were compared between the two groups. Results After treatment, the reduction rate of skin lesions in the observation group was higher than that in the control group, the skin lesion score was higher than that in the control group, and the total effective rate of treatment was higher than that in the control group (P<0.05). The incidence of adverse reactions and complications in the observation group was lower than that in the control group (P<0.05). The scores of skin smoothness, color and elasticity in the observation group were higher than those in the control group, and the improvement rate of aesthetics was higher than that in the control group (P<0.05). Conclusion Heated needle combined with ALA photodynamic therapy has good clinical effect and safety in the treatment of moderate to severe acne, and can effectively improve the skin condition and quality of life of patients, which is worthy of clinical application.