Adult-acquired flatfoot deformity (AAFD), which is mainly caused by posterior tibial tendon dysfunction (PTTD), is a common foot and ankle disease, and most of the deformities are flexible. How to explain the pathogenesis of AAFD and choose proper surgical treatment for the deformity has become a hot research focus nowadays. With the development of in vitro modeling technique for flatfoot, the accuracy and repeatability of the biomechanical tests have been gradually recognized, and the research results have also provided important theoretical basis for the clinical treatment of flatfoot deformity. In this article, the biomechanical mechanism of AAFD caused by PTTD, and the various modeling methods of flatfoot based on cadaver or finite element model were veviewed. The biomechanical characteristics of different reconstruction procedures in relative basic researches on flatfoot deformity were also analyzed and compared. The author believes that on the basis of simulating the dynamic stability of foot by tendon loading, the in vitro model of flexible flatfoot established by selective ligaments section is more reliable, and the reconstruction procedure adopted by various flatfoot models has different biomechanical characteristics. The soft tissue reconstruction and the bony procedures should be performed at the same time, and individual bony procedures should be chosen based on the degree and feature of the deformity.