Adult acquired flatfoot differs from pediatric flatfoot in that adult acquired flatfoot is caused by a variety of etiologies including degeneration, trauma, diabetes, rheumatoid arthritis, neuropathic lesions, tumors, and posterior tibial tendon dysfunction (PTTD). Clinical manifestations are: forefoot abduction and valgus, shortening of the lateral column of the foot, laxity of the midfoot, failure to lock the mid-tarsal joint, damage to the posterior tibial tendon, spring ligament and deltoid ligament, heel valgus, anterior rotation of the subtalar joint, degeneration of the subtalar and talar navicular joints. Specialists, based on the clinical manifestations and auxiliary examinations of adult acquired flatfoot, need to carry out scientific staging and select the appropriate treatment according to the corresponding staging in order to maximize the correction of deformity and relief of pain while preserving the function of the foot joint.