The assessment of flexibility of scoliosis is a conventional preoperative examination for adolescent idiopathic scoliosis, and it is important in selecting fusion level, deciding surgical approach, and predicting postoperative correction. With the innovation of orthopaedic concepts and the continuous development of internal fixation orthopaedic instruments, the commonly used methods for assessing scoliosis flexibility, including supine side-bending, fulcrum-bending and traction, however, have showed some disadvantages such as poor predictability, inconsistent evaluative criteria and radiation exposure. Therefore, it is important to choose a suitable method to evaluate the flexibility of scoliosis according to the clinical characteristics. This paper reviews the influencing factors and different evaluation methods for the flexibility of adolescent idiopathic scoliosis.