1. A method for producing a 3D facial expression animation using a single facial video stream, comprising: producing a representative joint focused on a major expression producing element in a 3D standard facial model; producing a statistical feature-point model of various facial expressions of different people in the 3D standard facial model; moving each feature-point of the statistical feature-point model by tracking a change in facial expressions of the single facial video stream; calculating a transformation coefficient of the representative joint corresponding to a variation of the feature-point of the 3D standard facial model according to the change in facial expressions of the single facial video stream; and producing a 3D facial expression animation by applying the calculated transformation coefficient to transform the representative joint, wherein the statistical feature-point model includes an average position shape of feature-points, a feature-point distribution model and an average texture information of each of the feature-points, and wherein the statistical feature-point model is used to determine an initial position of the each feature-point and a data for tracking the each feature-point of the single facial video stream.