Low level laser therapy (LLLT) has been widely used in the oral field. Its operation is relatively simple and non-invasive. Studies have shown that LLLT has the ability of anti-inflammatory, relieving pain, accelerating tissue healing and biological regulation. Some studies have suggested that the cellular molecular mechanism of LLLT is mainly related to the number and activity of mitochondria. It can regulate cell metabolism by increasing ATP production. Many scholars believe that LLLT can accelerate orthodontic tooth movement and alveolar bone remodeling, including the increase of the number of osteoclasts and osteoblasts and the deposition of collagen, accelerate the speed of tooth movement and shorten the orthodontic treatment course. It is of great clinical and scientific significance to study the application of LLLT in orthodontic tooth movement. Combined with references, the mechanism of LLLT and its application in orthodontic tooth movement were reviewed.