We studied tongue shapes extracted from X-ray films which were taken during the process of mandarin Chinese articulation. Through factor analysis, we built an eight-parameter-driven tongue articulation model. This study reveals that the front of the tongue has large horizontal movement; the blade of the tongue has large vertical movement; whereas the back, as well as the root, of the tongue has small movement both horizontally and vertically. This model can be used to drive a 3D tongue model to control its articulatory behavior.