The purpose of this study is to examine the impact and mechanisms of social media on branding in small and medium-sized catering firms. The paper identifies the importance of SMEs in today's market and the rise of social media in brand building. The research question of this paper is "how social media affects brand building in small and medium-sized catering enterprises", which aims to reveal the mechanism of its influence and provide practical guidance. This study adopts a theoretical research method, through literature review and theoretical analysis, to systematically sort out the relevant theories of brand building in small and medium-sized catering enterprises and the role of social media. It is found that social media has an important impact on brand building, including enhancing brand awareness, strengthening brand loyalty, and reinforcing brand storytelling. Finally, this study summarises the key role of social media in brand building of small and medium-sized catering enterprises and provides guidance for practice, while looking forward to future research directions.