Internet of Things (IoT) is an emerging trend referring to an interconnected network of ubiquitous intelligence. It is a revolution for Internet, computing and communication. Further extensions of IoT, Social Internet of Things (SIoT) provides a platform for people posting messages and photos, sharing knowledge, and connecting with each other. It is effective and efficient for people to manage their interpersonal relations through SIoT, but produces stress and tension issue coincidentally. Therefore, this study explores how users share knowledge through assessment and response under stress cognition. Three demand appraisals and three coping strategies are proposed to discuss user's behaviour on knowledge sharing, and Smart-PLS is used to test the conceptual framework. Results show that self-protection, anxiety, and avoidance increase when members of the community are threatened or injured. Nevertheless, members with high self-efficacy could reduce anxiety production and improve self-protection. Consequently, the purpose of knowledge sharing is achieved. This study discusses users' psychological perspectives when participating in the SIoT. It provides a better understanding of the human activities on the Internet through the SIot. Meanwhile, further prediction of users' behavior of knowledge sharing provides benefits and opportunities for businesses to establish their marketing strategy.