Objective: To investigate the correlation between morphological stages of midpalatal suture (MPS) and Demirjian dental age.Methods: In this retrospective study, 1 076 cone-beam CT (CBCT) images (female: 675, male: 401; age range: 6.0 to 21.0 years) were included. Horizontal view of each sample’s CBCT images was observed, each sample’s MPS stage was recorded, and dental age. MPS stage and dental age were ordered with categorical variables. Therefore, their correlation was investigated through Spearman correlation coefficient analysis and diagnostic test analysis.Results: (1) For left lower second premolar: 95.2% of those in dental age stage B-D were in MPS 1-2, accounting for the largest proportion. 85.3% of those in dental age stage E were in MPS 1-2, still accounting for the largest proportion. Another 14.7% were in MPS 3. 45.1% of those in dental age stage F were in MPS 3, 46.1% in MPS 1-2, and another 8.8% in MPS 4s1. 49.8% of those in dental age stage G were in MPS 3. 24.9% in MPS 4s1, and 18.9% in MPS 1-2. 80.1% of those in dental age stage H were in MPS 4-5. Another 16.3% were in MPS 3. (2) For left lower second molar: 89.7% of those in dental age stage B-D were in MPS 1-2, accounting for the largest proportion. 67.4% of those in dental age stage E were in MPS 1-2, still accounting for the largest proportion. Another 26.1% were in MPS 3. 55.3% of those in dental age stage F were in MPS 3, 34.2% in MPS 1-2, and another 10.5% in MPS 4s1. 50.7% of those in dental age stage G were in MPS 3, 24.3% in MPS 4s1, and 16.8% in MPS 1-2. 83.8% of those in dental age stage H were in MPS 4-5, another 14.2% were in MPS 3. (3) To diagnose MPS stage with dental age, diagnostic pairs with good performance included: Dental age of left lower second molar-MPS: H-4s2, H-5, D-1; Dental age of left lower second premolar-MPS: H-4s2, H-5, G-3. Other diagnostic pairs were of ordinary diagnostic efficiency. (4) For dental age-MPS Spearman correlation analysis, dental age of left lower second molar-MPS had the highest Spearman coefficient (0.68), dental age of left lower second premolar-MPS was the second high (0.64). (5) Dental age stage H of left lower second molar or left lower second premolar indicated that the individual was later than MPS 4s2.Conclusion: Dental age’s diagnostic efficiency for MPS stage is ordinary on the whole, except for some pairs with good performance. Therefore, pre-treatment CBCT examination should be considered as assistance for evaluating maturation and fusion status of midpalatal suture.