Objective: We used cone-beam computed tomography to observe the calcification time of the midpalatal suture, evaluate the relationship between the calcification and age, sex. It 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. Evaluated the relationship between the calcification degree and age, sex. Results: The degree of calcification of the midpalatal suture increased with age. Complete calcification was first seen in a 10-year-old woman, approximately 20% of the patients aged 15 had calcified, and about 50% of the patients aged 18 had calcified. However, some cases of 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 females, but there was no difference in the stages of calcification between males and females before and after adolescence. Conclusions: 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. Male calcified later in adolescence. It suggested that individual assessment is essential before rapid maxillary expansion.