As we all know, in the family of electromagnetic spectrum, γ-ray, X-ray, ultraviolet, visible, infrared and microwave have all been playing an important role in the field of medical treatment. However, terahertz (THz) radiation which is between microwave and infrared is still in the early stages of development. THz wave with specific wavelength is focused into a line, called THz needle. For sleep therapy research, the THz needle regulating sleep clinical efficacy is explored. After clinical experiment, it is found that THz waves can effectively improve the quality of sleep. For further study of the mechanism of the interaction of THz radiation with the human body, we specifically observe some interesting details of clinical trials. In the photoplethysmography (PPG) signal after irradiation THz wave, a second small peak appears, and the patient′s serum potassium concentration increases. This study not only provides an effective, non-invasive physical method for sleep therapy, but also offers THz technology itself new research materials.