Objective To explore the effect of botulinum toxin injection therapy on skin tightness and wrinkle improvement in middle-aged and elderly patients with facial skin aging. Methods A total of 84 middle-aged and elderly patients with skin laxity admitted to the Department of Medical Cosmetology, the First People's Hospital of Shangqiu from January 2024 to January 2025 were selected as the research subjects. According to the random number table method, they were divided into the control group and the experimental group, with 42 patients in each group. The control group was treated with gene-activating anti-wrinkle peptides, and the experimental group was treated with botulinum toxin injection. The skin condition, wrinkle improvement, satisfaction and complications were compared between the two groups. Results After treatment, the scores of skin moisture and elasticity in the experimental group were higher than those in the control group, and the scores of oil and dark spots were lower than those in the control group (P <0.05). The excellent and good rate of wrinkle improvement in the experimental group was 97.62%, which was higher than 80.95% in the control group (P <0.05). The satisfaction rate in the experimental group was 95.24%, which was higher than 78.57% in the control group (P <0.05). The incidence of complications in the experimental group was 0, which was lower than 9.52% in the control group (P <0.05). Conclusion The application of botulinum toxin injection therapy in middle-aged and elderly patients with skin laxity has a good effect, which can effectively improve the skin condition of patients, enhance the wrinkle improvement, and the incidence of complications after treatment is low, with higher patient satisfaction.