Abstract: Objective To explore the changes of collagen fibrosis in the vulva skin of SD rats with lichen simplex chronicus (LSC) after focused ultrasound therapy and explore the mechanism by which focused ultrasound reduces the recurrence of vulvar LSC. Methods Fifty female SD rat models of vulvar LSC were established and randomly divided into the treatment group and the control group (n=25) for treatment with focused ultrasound and sham treatment, respectively. Before and after the treatment, vulvar skin tissues were sampled to observe the pathological changes with HE staining and assess the density of collagen fibers using Masson staining. The ultrastructure of the collagen fibers in the superficial dermis was observed using transmission electron microscopy. The expressions of notch1 and c-fos in the vulvar tissue were detected by immunohistochemistry and Western blotting. Results After 4 weeks of focused ultrasound therapy, 16% (4/25) of the rats in the treatment group showed lesion progression to LSIL, 4% (1/25) still had LSC, and 80% (20/25) showed normal vulvar skin. In the control group, progression to LSIL occurred in 19 (76%) rats, 3 (12%) rats still showed LSC, and only 3 (12%) had normal vulvar skin. The difference in the cure rate differed significantly between the two groups (P<0.05). The density of collagen fibers in the superficial dermis and the expressions of notch1 and c-fos in the vulvar skin were significantly lower in the treatment group than in the control group (P<0.05). Conclusion Focused ultrasound therapy can inhibit superficial collagen fibrosis of the dermis by lowering the expressions of notch1 and c-fos in the vulvar skin to reduce the recurrence of vulvar LSC in rats.