Objective To investigate the hard and soft tissue changes following the treatment of Class Ⅱ division 1 malocclusion using Twin-block appliance. Methods 50 Class Ⅱ division 1 malocclusion subjects whose handwrist radiographs were in FG-G stage were selected. One group（27 patients） was treated with Twin-block appliance, the other group（23 patients） was observed without treatment. The acquired data of cephalometric of two groups were analyzed statistically with SPSS 11.0. Results Soft tissue changes, Ls-E, Li-E, U1-Stms, Stms-Stmi, NsLs-FH, LsNsLi, LsNsPg’, the angle of H decreased. Sn-Stms, Stmi-Me’, Ns-Me’, Sn-Me’, NsLi-FH, NsPg’-FH, A’Ls-FH, B’Li- FH, LiB’Pg’, CmSnLs, GSnPg’, the angle of Z increased, there was statistically significant difference（P
