This study provides a comprehensive review of ultrasonic welding research in molecular dynamics simulations, encompassing the latest advancements by scholars worldwide. Compared to traditional welding methods, ultrasonic welding offers advantages such as faster processing speed, higher mechanical strength, and environmentally friendly characteristics. However, its process parameters are subject to multiple influencing factors. Molecular dynamics simulations enable the detailed visualization of material interactions and structural changes at atomic/molecular levels during ultrasonic welding. These simulations not only predict how different process parameters affect weld quality but also facilitate the rapid identification of viable solutions, thereby reducing experimental iterations and lowering R&D costs. This review delves into the core theoretical issues pertaining to ultrasonic welding, providing robust support for practical applications. Additionally, specific optimization strategies are proposed to enhance welding performance and efficiency, promoting sustainable development in related industries. Future research could focus on exploring ultrasonic welding mechanisms under complex structures and multi-component systems.