In early 2025, a significant influx of “TikTok refugees”—predominantly American netizens—migrated to the Chinese social platform Xiaohongshu, creating a notable cross-cultural communication phenomenon. Framed by emotional contagion theory, this study examines the mechanisms of emotional transmission through three dimensions: emotional arousal, emotional resonance, and emotional diffusion. Key findings reveal that (1) cross-cultural emotional arousal was achieved through “refugee” narratives and cultural resistance; (2) emotional resonance emerged via symbolic consensus-building and intersubjective communication; (3) emotional diffusion occurred through collective memory activation, cultural rituals, and innovative visual symbols. The study identifies critical influencing factors, including decoding differences in high/low-context communication, “echo chamber” effects, and cultural discount, with national media environments serving as a significant variable. The research proposes strategies for fostering positive emotional contagion in cross-cultural contexts: reducing linguistic and symbolic decoding barriers to alleviate cultural discount, leveraging algorithm technologies to mitigate negative emotional transmission risks, and facilitating emotional synchronization between different “public opinion spheres.”