It is clinically important to accurately predict facial soft tissue changes following bone movements in orthognathic surgical planning. However, the current simulation methods are still problematic, especially in clinically critical regions, e.g., the nose, lips and chin. In this study, finite element method (FEM) simulation model with realistic tissue sliding effects was developed to increase the prediction accuracy in critical regions. First, the facial soft-tissuechange following bone movements was simulated using FEM with sliding effect with nodal force constraint. Subsequently, sliding effect with a nodal displacement constraint was implemented by reassigning the bone-soft tissue mapping and boundary condition for realistic sliding movement simulation. Our method has been quantitatively evaluated using 30 patient datasets. The FEM simulation method with the realistic sliding effects showed significant accuracy improvement in the whole face and the critical areas (i.e., lips, nose and chin) in comparison with the traditional FEM method.