Since the outbreak of the COVID-19 pandemic, social media are used frequently in the process of teaching and learning interaction, which not only endows learning with sociality, but also poses challenges to students' autonomous learning behavior. To identify the influencing factors of motivation regulation in blended learning environments, we need to pay more attention needs to the mechanisms and strategies that support students' long-term interests. The results revealed that social interaction and perceived playfulness are important factors affecting students' motivation regulation, and teachers' support of autonomy, emotion, and ability play a regulatory role. The results present internal and external driving forces of students' motivation regulation, which are useful for educators to understand the plasticity of motivation and the inequality of learning achievements of specific student groups. Therefore, teachers are required to play a more supportive role in the social learning environment based on game thinking and interactive design to enhance students' learning motivation.