Flatfoot is a kind of foot deformity with the collapse of the medial longitudinal arch of the foot as the main manifestation, and the determination of flatfoot can be made through the examination methods such as footprint method, CT, X-ray flat film and so on. The details are as follows: 1. Footprint method: stand on a white paper after dipping the foot in water or sealing clay, measure the ratio between the width of the blank area of the arch and the narrowest area of the footprint, the normal ratio is 2:1, and the flat foot is obviously smaller than this ratio. 2.CT: CT scan can show the bony anatomy and determine the angle of the foot arch, the normal angle is 150 to 175 degrees, if it is smaller than the normal angle of the foot arch, it can be judged as flat foot. 3. X-ray film: A lateral x-ray film of the foot can show the structure of the arch and measure the height of the arch, the normal value is 14 to 18 millimeters, if it is less than the normal value, it can be judged as flat feet. If the examination reveals the existence of flat feet, it is recommended that the patient seek medical treatment in time to avoid adverse consequences.