Objective To explore the efficacy of urethral plate incision and onlay island flap in one-stage treatment of children with severe hypospadias and its impact on aesthetic satisfaction. Methods A total of 84 children with severe hypospadias admitted to the Affiliated Hospital of Guilin Medical University from April 2022 to April 2024 were selected and randomly divided into control group (n =42) and observation group (n =42). The control group was given preputial island flap urethroplasty treatment, and the observation group was given urethral plate incision and onlay island flap in one-stage treatment. The surgical success rate, clinical surgical indicators, aesthetic satisfaction and complication rate were compared between the two groups. Results The surgical success rate of the observation group (95.24%) was higher than that of the control group (83.33%) (P <0.05). The operation time of the observation group was longer than that of the control group, while the ambulation time and hospitalization time were shorter than those of the control group (P <0.05). The aesthetic satisfaction of the observation group (97.62%) was higher than that of the control group (85.71%) (P <0.05). The complication rate of the observation group (4.76%) was lower than that of the control group (11.90%) (P <0.05). Conclusion Urethral plate incision and onlay island flap in one-stage treatment has a good effect in the treatment of severe hypospadias. It can improve the aesthetic satisfaction and the surgical success rate, shorten the postoperative recovery time, and reduce the complication rate, which is worthy of clinical application.