Background This study was to evaluate the diagnostic significance of Magnetic Resonance Imaging (MRI) in distinguishing temporomandibular disorders (TMD). Methods A total of 684 patients with TMD were included in the study. Diagnosis for TMD was conducted according to the international criteria. Two professional radiologists were selected for professional training, and the Kappa values were compared for the diagnosis results to determine the consistency of the diagnosis. Then MRI images of these 684 patients were analyzed and the diagnosis results were obtained. Results MRI can be used for the diagnosis of TMD. There were significantly more females (518 cases) than males (166 cases) with TMD; Disc displacement with/without reduction is more common in the youth group, with the majority aged 20-30 years. The highest incidence of temporomandibular joint osteoarthrosis is in the 60-year-old age group, followed by the 70-year-old age group. Conclusions Bilateral temporomandibular joint MRI can clearly show their changes; there are significantly more female with TMD than male; osteoarthritis has a significant correlation with age.