A novel technique is proposed to make realistic facial animation driven by motion capture data. First, one's facial expressions are recorded using Oxford Metrics' VICON 8 optical motion capture system, where 23 optical markers are attached on one's face. The captured 3D motion data are then processed to eliminate 3D global head motion by finding the pivot point for rotation. These processed 3D motion data can be directly applied to a head model. A two and half dimension facial model is used here for implementation because it combines good features from both 2D mesh and 3D model: simple, vivid and natural, when small-scale rotation is applied. An interpolation function is employed to calculate the offsets of other unconstrained mesh vertices; furthermore, a face is divided into several regions and force constraints are applied to limit the displacement of vertices on the mesh depending on the region to make the animation more natural. The system has an update rate of over 30 frames/second on a Pentium III 500MHz PC with an OpenGL acceleration card.