Flat feet are a kind of foot deformity that is caused by congenital or postural factors, resulting in low or disappearing arches, outward turning of the affected foot, and collapse of the foot arch when standing or walking, which results in fatigue or pain. Flat feet are categorized into congenital and acquired factors. Congenital factors mainly include oversized bony tuberosity, heel valgus, and muscle laxity. Acquired factors include foot trauma, chronic strain, and injury to the foot bones. It leads to arch collapse, pain or fatigue when walking. The main symptoms of flat feet are pain on the medial and posterior side of the rear foot, and swelling outside the joints that are easily fatigued and painful when walking. Symptoms can be improved and relieved by localized massage and wearing corrective shoes, and if they cannot be improved, they should be treated with bony surgery or soft tissue transfer repair. Flat feet in daily life should avoid long distance or strenuous walking, usually can choose more comfortable flat shoes to relieve foot fatigue.