To investigate the biomechanical influences on two different cleft maxillary 3D finite element models pre- and post-alveolar bone graft, we developed a cleft palate bony model from a 17 year cleft palate male CT scan data and built an alveolar bone-grafted cleft maxillary 3D finite element model through gluing the graft model. Apply vector lip force on the anterior face of the models. Study the press (including S3 principal, S1 principal, von Mises and shear) distribution properties and localized area. The results suggested that the press principal spreads along the alveolar ridge and formed several focused areas. After bone grafted, the shear stress tends to be evenly. The grafted alveolar could resist the medially deformation of alveolar crest and the shear stress to the nasal base bony structure. The conclusions from results demonstrated that the deformation of alveolar ridge is possibly due to the lip pressure after the lip repair. The shear stress along the alveolar ridge could cause the severity of the dentition. The grafted bony structure could even the shear stress distribution evenly other than the distribution properties.