Objective To explore the application effect of new micro-focused ultrasound technology on improving fat accumulation in mandibular margin. Methods From November 2022 to November 2023, 52 patients who underwent mandibular fat accumulation in Ningbo Jiahe Plastic Surgery Hospital were selected as the research objects. According to the random number table method, the patients were divided into control group and study group, with 26 patients in each group. The control group was treated with conventional botulinum toxin microinjection, and the study group was treated with new micro-focused ultrasound. The clinical efficacy, facial aesthetics, facial rejuvenation and adverse reactions were compared between the two groups. Results The obvions effective rate of treatment in the study group was 73.08%, which was higher than 65.38% in the control group, but the difference was not statistically significant (P >0.05). After treatment, the facial beauty scores of the two groups increased, but the difference was not statistically significant between the two groups (P >0.05). After treatment, the WSRS score and FWS score of the two groups decreased, but the difference was not statistically significant between the two groups (P >0.05). The incidence of adverse reactions in the study group was lower than that in the control group, but the difference was not statistically significant (P >0.05). Conclusion The application of new micro-focused ultrasound technology in the treatment of fat accumulation at the mandibular margin is effective, which can improve the facial aesthetics and promote the improvement of skin elasticity. It is a non-invasive, safe and effective treatment technology with high application value.