Objective To compare the efficacy and safety of Q-switched Nd:YAG laser with different spot parameters in the treatment of nevus fusco-caeruleus zygomaticus. Methods A total of 200 patients with nevus fusco-caeruleus zygomaticus admitted to our hospital from January 2023 to December 2025 were selected as the research subjects, and they were divided into the control group and the observation group by the random number table method, with 100 patients in each group. Both groups received Q-switched Nd:YAG laser treatment. The control group was treated with a spot diameter of 4 mm and an energy density of 3.5-5.0 J/cm2, and the observation group was treated with a spot diameter of 3 mm and an energy density of 7.0-9.0 J/cm2. The clinical efficacy, adverse reactions and satisfaction were compared between the two groups. Results The cure rate (48.00%) and total effective rate (97.00%) in the observation group were higher than those in the control group (30.00%, 90.00%) (P <0.05). The incidence of adverse reactions in the observation group was higher than that in the control group (P <0.05). The satisfaction rate of the observation group (86.00%) was higher than that of the control group (74.00%) (P <0.05). Conclusion For patients with nevus fusco-caeruleus zygomaticus, Q-switched Nd:YAG laser with a 3 mm spot diameter and energy density of 7.0-9.0 J/cm2 can improve therapeutic effect and patient satisfaction, but it increases the incidence of adverse reactions such as pigmentation and blisters. Clinical parameters should be selected individually according to the patient's skin type, lesion depth and tolerance.