The classification of food impaction is not consistent nationally or internationally. Hirschfeld classified food impaction into five categories according to the etiology of food impaction: abrasion type, no contact with adjacent surfaces, teeth protruding from the planes, congenital dental anomalies, and incorrectly made fillings; each type is divided into different subtypes, and this classification is not adopted by domestic textbooks because it is more complicated, although it starts from the etiology. Domestic scholars according to the direction of food into the interdental space will be divided into vertical type and horizontal type of food impaction, the classification is intuitively easy to be recognized, for decades has been used as a classical typology, but the horizontal type of food impaction is caused by gingival recession, and gingival recession can not be restored, so the horizontal type of food impaction is difficult to treat, indirectly leading to the untreatable food impaction, apparently the horizontal type of food impaction has not been seriously proposed. It is obvious that the proposal of horizontal food impaction has not been seriously investigated. In 1994, Zheng Dize proposed a different classification method, according to the scope of embolism into limited type, partial type and extensive type, and proposed the corresponding treatment measures. This classification is of little clinical guidance. Recently, the authors concluded that the root cause of food impaction lies in the loss of contact between adjacent surfaces, and from the etiology of food impaction, food impaction is classified into static gap food impaction and motor gap food impaction. Food impaction occurs when there is a contact relationship in the non-occlusal state, but the contact area is separated briefly during the occlusal movement. With the correct classification, the treatment of food impaction is easy.