Objective To compare the efficacy and safety of simultaneous injection versus interval injection of hyaluronic acid combined with type A botulinum toxin in the treatment of moderate to severe glabellar lines. Methods A total of 112 patients with moderate to severe glabellar lines admitted to the Micro-plastic Surgery Department of Shanghai Time Plastic Surgery Hospital from March 2022 to March 2025 were selected. According to different injection timings, they were divided into the control group (n =57) and the observation group (n =55). The control group received simultaneous injection scheme: sodium hyaluronate was injected immediately in the same treatment area after the injection of type A botulinum toxin. The observation group received interval injection scheme: type A botulinum toxin was injected first, muscle relaxation was evaluated at 1 week after injection, and then sodium hyaluronate was injected. The wrinkle severity, glabellar line improvement effect, negative emotions complication rate and quality of life were compared between the two groups. Results The scores of WSRS in the observation group at 4 weeks and 12 weeks after treatment were lower than those in the control group (P <0.05). The total effective rate of glabellar line improvement in the observation group (92.73%) was higher than that in the control group (77.19%) (P<0.05). The scores of SAS and SDS in the observation group after treatment were lower than those in the control group (P <0.05). The incidence of complications in the observation group was lower than that in the control group (P <0.05). The scores of each dimension of quality of life in the observation group after treatment were lower than those in the control group (P <0.05). Conclusion The interval injection scheme of hyaluronic acid combined with type A botulinum toxin is superior to the simultaneous injection scheme in the treatment of moderate to severe glabellar lines. It can effectively reduce the severity of wrinkles, improve the total effective rate of glabellar line improvement, help to reduce the incidence of complications, and enhance quality of life, with high treatment efficacy and safety.