Objective: To evaluate the morphology of dental arches. Methods: 62 (male: 36, female: 26) paired casts having normal dentitions and occlusion were selected for study. 17 point were designated as reference points. We measured and evaluated seven items such as , [1]angle I2R-CR-P1R + angle I2L-CL-P1L, [2]A-B/CR-CL, [3] 180°-angleCR-A-CL, [4]A-E/CR-CL, [5]A-B/M2R-M2L, [6](rq5-rq4)R+(rq5-rq4)L, and [7] for the differentiation of type I and type II round-square arches by relating the bilateral contour and position of break line P1-P2-M1-M2 (i) to line P1-M2 (ii). The data of items [1], [2], [3], [4], [5] and [6] were further standardized and summarized into three components: 1) the curvature of the anterior teeth, 2) the curvilinear contour of the dental arch, and 3) the length-to-width ratio of the dental arch. Results: 1) 60% of the maxillary dentitions were round-square arches which showed no prominent component,2) square maxillary arches distinctly showed a small item [1] item; 3) round arches were characteristic by small item [6] value,and 4) round V-shaped arches had large [2], [3] and [4] values. Conclusions: We concluded that Parameter [1],[2],[3],[4],[5],[6] and [7] were summarized into three principal components (first principal component, second principal component and third principal component). Through three component analysis, we can quickly evaluate the morphology of the dental arches simply and validity. And we can also know the characteristics of maxillary dental arches.