Synthetic biology has an important impact on biology research since its birth. Applying the thought and methods that reference from electrical engineering, synthetic biology uncovers many regulatory mechanisms of life systems, transforms and expands a series of biological components. Therefore, it brings a wide range of biomedical applications, including providing new ideas for disease diagnosis and treatment. This review describes the latest advances in the field of disease diagnosis and therapy based on mammalian cell or bacterial synthetic gene circuits, and provides new ideas for future smart therapy design.