Digital polysomnography is the common diagnostic tool for sleep disorders. Adequate operation of polysomnography is essential and related to the quality of diagnosis and treatments of sleep disorders. On the other hand, due to convenience and comfortability, the universality of HSAT (Home sleep apnea test) is increased in recent years. The principles of digital polysomnography and the knowledge of home testing equipment are essential core capabilities for sleep therapists. In this lecture, we can learn about the following contents: 1) The role of sleep therapists in sleep medicine center. 2) Principles of digital polysomnography. 3) Principles of adjusting parameters of polysomnography. 4) Application of polysomnography in diagnosis of sleep disorders. 5) Interpretation of the report of polysomnography. 6) Principles and application of HSAT in diagnosis of sleep disorders. 7) Common troubleshooting and the solutions of troubleshooting in polysomnography. Above contents of this lecture will contribute to the enhancement of the core capabilities for sleep theapists.