Factors affecting the retention of the complete denture include: 1, good alveolar conditions, retention is better, the alveolar is relatively low and flat, retention is worse; 2, missing teeth for a longer period of time, the tongue becomes larger, the buccal muscle collapses, the first wear can not control the denture well, which has a greater impact on retention; 3, related to the age of the patient: young patients are easy to adapt, older patients are more difficult to adapt; 4, patients who have been wearing dentures for a long time have a more stable retention; 5, the doctor factor: imbalance in the production can affect retention.