Objective   To explore the stress and displacement distribution of submaxilla subjected to Forsus

and investigate the optimal angle of orthopedic force in order to provide biomechanical basis for new  appliances designation.    Methods   A health 12-year-old clinical volunteer with Angle classⅡ malocclusion was subjected. Helical CT and 3-D image technique were used to finish the primary model reconstruction. And a 3-D finite element (FE) model of the submaxilla

dentition and archwires and brackets was constructed with ABAQUS software. Then Forsus orthopedic force application based on the FE model were simulated under 5 different designed conditions.    Results   Under all 5 loading conditions

the Von Mises equivalent stresses level on the dentition and archwires and brackets are higher than on the submaxilla

the highest stress was on the archwires and brackets. Stress centralization on the submaxilla mostly located at the condylar and alveolar ridge

the highest stress of the submaxilla was on the condylar

and the largest displacement of submaxilla was on the chin basically. Plastical strain were appeared on the condylar.    Conclusion   The optimal angle of orthopedic forsus force is between 0° and 25°.