With the popularization and development of social media, adolescence has become an important platform for adolescents to express their views, exchange information and participate in society. The purpose of this paper is to explore in depth adolescents' behavioral responses to public events on social media and their guiding trends and to analyze adolescents' motivations for using social media, the manifestation of public events on social media, the application of social movement theories in social media research, and the modern transformation of public sphere theories. Using a mixed-methods design that combines quantitative and qualitative data analysis, this study provides a comprehensive picture of adolescents' behavioral patterns, motivations for participation, and social impact on social media, as well as their roles and challenges in public discourse. The study revealed that adolescents respond to a variety of types of public events, including posting, commenting, sharing, and engaging in hashtags. Adolescents' interactive behaviors on social media information diffusion, opinion formation, and social mobilization are important social impacts of adolescents' social media behaviors. They accelerate the spread of information through sharing and retweeting, participate in the discussion of public issues and have a direct impact on the formation of public opinion. In addition, social media has become an effective tool for mobilizing social action, and adolescents promote practical action and participation in public issues by interacting with and organizing online activities. This study proposes a series of coping strategies, including improving users' media literacy and information discernment, social media platforms to strengthen the regulation and auditing of information dissemination, and the government and the community to strengthen the regulation and governance of the social media field. This study provides new perspectives for understanding adolescents' social participation in the digital age, showing how social media, as a new public sphere, affects public discourse, social mobilization, and the formation of civic identity. The findings not only provide rich empirical material for sociological theories but also provide valuable insights for promoting social public participation, improving information quality, and advancing social progress. Future research can further explore the impact of social media on adolescents' social participation in different cultural and social contexts, as well as how to optimize the efficacy of social media as a platform for public discourse and social mobilization through educational and policy interventions.