With the development of society and the progress of medicine, hair health has become more and more concerned by human beings, and “hair growth” has become a major topic of research for dermatologists. “Laser hair regrowth” has become an epoch-making innovation in the medical field, and we will introduce the clinical mechanism of laser hair regrowth in detail below. What is “hair loss”? Alopecia areata is a clinical condition that includes androgenetic alopecia, alopecia areata, alopecia at rest, alopecia during the anagen phase, alopecia due to hair shaft disease, mechanical alopecia, and plucking fetish. Scalp subcutaneous blood flow studies show that subcutaneous blood flow in normal people is 10 times more than subcutaneous blood flow in other parts of the scalp and 2.6 times less than the normal group in baldness, these studies suggest that local blood supply has a close relationship with hair loss. The principle of laser hair growth: 1, accelerate the blood circulation of the scalp, promote metabolism; 2, stimulate the hair follicles, 83% of the resting state of the hair follicles will be activated to the active phase, stop hair loss; 3, regulate the oil secretion of excessive oil is the cause of hair loss; 4, strengthen the immune function of the body cells; 5, promote the health of the scalp. The role of laser hair growth: 1, hair breeding: the use of 670nm wavelength of bio-stimulation characteristics, accelerate hair follicle cell division, promote hair growth, increase the vitality of hair follicles. 2, hair health: 670nm laser makes vascular expansion, promote scalp blood circulation, so that the supply of nutrients to the hair follicle is sufficient, convey more easily, the amino acids needed for hair growth can be more quickly supplied. Laser hair growth specific treatment: 16 weeks of treatment with Derma 670nm red light, 20-30 minutes twice a week for weeks 1-5, and 30 minutes once a week for weeks 6-16. The average number of hair growth was 37.79%. In order to promote hair growth, traditional medicine is based on a combination of oral and topical medication, but now medicine has given a new concept to provide a new treatment method for hair loss patients by combining the medication with physical therapy – 670nm laser irradiation treatment.