ObjectiveTo observe the efficacy and safety of lacosamide (LCM) as a monotherapy or as an add-on in the treatment of focal epilepsy in children aged 4 months to 4 years. MethodsThe study included 20 children with focal epilepsy who received oral LCM monotherapy or add-on therapy in Children's Hospital Affiliated to Soochow University from March 2022 to September 2022, including 9 males and 11 females with an average age of (22.4±13.0) months. The curative effects and adverse reactions at 1, 2, 3, 4, and 6 months after LCM treatment were analyzed. The initial dose of LCM was 2 mg/(kg·d) and increased by 2 mg/(kg·d) every week, maintenance dose 6 ~ 12mg/(kg·d). Results During the follow-up period of this study, the total effective cases were 17 (85.00%), and the number of control-free cases was 15 (75.00%). Conclusion LCM can effectively reduce the frequency of epileptic seizures in the monotherapy or add-on treatment of infants and young children with focal epilepsy, with few adverse reactions and high retention rate, which has high clinical application value.