Objective：This study aims to observe the calcification time of the midpalatal suture，evaluate the relationship between the calcification and age or gender by using cone-beam computed tomography，which can be used for individual assessment and guidance before rapid maxillary expansion in adults and adolescents. Methods：The CBCT images of 211 subjects（4.2-43.8 years old）were divided into five stages according to the degree of the midpalatal suture calcification. The relationship between the calcification degree and age or gender was evaluated. Results：Calcification degree of midpalatal suture increased with age. Complete calcification was first seen in a 10-year-old female，approximately 50% of patients aged 15 had calcified. However，some uncalcified midpalatal suture were still found in adult patients，and the latest was found in a 37-year-old woman. Calcification of the palatal suture was later in adolescent males than in adolescent females，but there was no difference between males and females before and after adolescence. Conclusion：Calcification of the midpalatal suture is associated with age，and continues from age 10 to adulthood. But in some adult patients，the midpalatal suture is not calcified. Calcification of the midpalatal suture is later in adolescent males than in adolescent females. It suggested that individual assessment is essential before rapid maxillary expansion.