Objective To evaluate whether there was any difference on the clinical effects of Twin - block, Activator and Herbst appliances on the clinical effects of growing children with skeletal Class Ⅱ malocclusion. Methods 60 patients with skeletal Angle Class Ⅱ malocclusion were divided into three groups（Twin- block group, Activator group, Herbst group）, 20 in each group. The patients of three groups were respectively treated by Twinblock, Activator and Herbst appliances. The patients were 10- 13 years old（mean 11.6） before treatment, and were mainly with mandibular retrognathia. Data of pre- and post- treatment were measured and analyzed. Results There was statistically significance of ANB, SNB, Go- Gn, Co- Gn, L1-MP in sagittal changes, and N-Me, ANS-Me, S- Go, SN-MP, Co- Go in vertical changes after treatmen of three groups. Herbst group was more effective than Twin- block group and Activator group in the increase of L1-MP, but the effects on maxilla were not significant among them. There was no statisticall significance of Ptm- A, OB, N-Me, ANS-Me, S- Go and Co- Go between 3 groups. Conclusion Treatment effects of three different functional appliances（Twin- block, Activator and Herbst） are similar in the early treatment of skeletal Class Ⅱ malocclusion. Compared with Twin- block and Activator, Herbst has more effects on orthopedic of mandibular and lower anterior teeth.
