Objective To study the characteristics of the arch form of skeletal Class Ⅲ malocclusion and provide references for diagnosis and treatment plan. Methods 7 indexes in dental casts of 47 patients with skeletal Class Ⅲ malocclusion and 50 individuals with normal occlusion were measured respectively. And differences between corresponding upper and lower measurements were calculated. Independent samples t-test was employed for comparing between the two groups by SPSS 17.0. Results Compared with normal occlusion sample, Class Ⅲ malocclusion group had smaller anterior segment lengths and larger canine angles（P
