Objective To explore the effect of erbium fractional laser therapy on skin lesion severity in patients with rosacea. Methods A total of 68 patients with rosacea admitted to the Second Affiliated Hospital of Nanjing Medical University from February 2023 to May 2025 were selected, and they were divided into the control group and the observation group by the random number table method, with 34 patients in each group. The control group was treated with doxycycline tablets combined with metronidazole gel, and the observation group was treated with erbium fractional laser therapy. The skin lesion severity, treatment effect, skin physiological indicators and adverse reaction rate were compared between the two groups. Results The IGA score of the observation group after treatment was lower than that of the control group (P<0.05). The total effective rate of the observation group (94.12%) was higher than that of the control group (61.76%) (P<0.05). After treatment, the skin erythema index and transepidermal water loss of the observation group were lower than those of the control group, and the stratum corneum hydration was higher than that of the control group (P<0.05). The incidence of adverse reactions in the observation group (5.88%) was lower than that in the control group (38.24%) (P<0.05). Conclusion The application of erbium fractional laser therapy in patients with rosacea can effectively reduce skin lesion severity, improve the total effective rate of treatment, and optimize skin physiological indicators. The incidence of adverse reactions after treatment is low and the safety is good.