In this paper, a method for characterizing the morphological information of craniofacial structure using the tracings and cephalograms in posteroanterior view is proposed and the experimental results are analyzed. This is a retrospective study. In clinical practice of orthodontics, the cephalograms taken in lateral and posteroanterior views are often used. Here, the morphological analysis of craniofacial structure is characterized only in posteroanterior view. Firstly, the morphological feature parameters of cephalometric tracings are defined and extracted. Then, based on these parameters, the morphology of craniofacial structure in posteroanterior view is clustered using fuzzy c-means and ISODATA clustering method. In this study, the data sets of eighty tracings are investigated. From experimental results, the craniofacial structures are classified into six clusters. Each cluster has ten images, sixteen images, ten images, fifteen images, thirteen images, and sixteen images, respectively. The standard deviations for the landmark are all within 6 mm in each cluster. The morphological information can be further extended and used in cephalogram landmarking.