One of the core challenges faced by children with autism is repetitive motor behavior, which not only undermines their learning efficiency in the classroom but also makes it difficult for them to integrate smoothly into inclusive educational settings, thereby hindering their social adaptation and overall development. This study adopted a single-case design focusing on a first-grade student with autism enrolled in a mainstream class at Xiangxue Primary School, Huangpu District, Guangzhou. Functional behavior assessment was conducted to systematically observe and analyze the student’s repetitive motor behaviors in class, on the basis of which an intervention plan was developed and implemented. The intervention incorporated antecedent control, replacement behavior training, and consequence management, supplemented by collaboration between school and family. The findings indicated that the frequency of repetitive motor behaviors decreased significantly after the intervention, while the student demonstrated improved classroom participation and peer interaction; these positive effects were maintained during the follow-up phase. The study suggests that in inclusive education settings, interventions guided by functional behavior assessment can effectively reduce problem behaviors in children with autism and enhance their classroom engagement and learning adaptability.