The work aims to take the chair in the home environment as an interactive medium to develop a health promotion system that is more natural and adapted to the home environment in order to reduce the physical and mental health burden caused by the chronic stress of life. The users' behavioral activity of 'sitting' was used to characterize their physical and mental health and combined with digitally assisted mindfulness theory, the empirical study of the natural interaction of a smart chair in the home environment was carried out. A natural Human-Computer Interaction interface using the chair as both input and feedback was proposed. The natural dynamic mapping relationship between the users' body touch and breathing was utilized to guide the users through a mindfulness activity by changing the size of the airbag on the back of the chair.The validity and usability of the system can be demonstrated through the collection of objective physiological signals and subjective user-reported scales for different emotional states such as anxiety and relaxation. The system can effectively reduce stress and enhance users' emotional experience and also reflect users' behavioral states through indicators such as sitting duration and posture. In addition, it can contribute to the good development of mental and physical health, providing a reference for related designs.