Understanding the biomechanical properties of periodontal ligament is of great significance for orthodontic treatment. Due to the complexity of periodontal ligament structures, previous studies mainly used in vitro experiments, which had limitations. In order to obtain accurate and actual data, in vivo experiments on biomechanical properties of periodontal ligaments will become a trend of development in the future. In this article, the method, types, progress, advantages and disadvantages of in vivo experiments on biomechanical properties of periodontal ligaments were reviewed and prospected.