This study proposes an approach to the generation of video-based movement epenthesis for sign language, and concentrates on a spatial interpolation approach using a Non-Uniform Rational B-spline (NURBS) function to produce a smooth interpolation curve. To generate movement epenthesis, the beginning and end "cut points" are determined based on the concatenation cost, which is a linear combination of the distance, smoothness and image distortion costs. An image component overlapping procedure is also employed to yield a smooth sign video output. To evaluate the proposed approach, a set of sign video databases is collected and preprocessed with image calibration, content annotation and principle component analysis (PCA). Evaluation results demonstrate that the synthesized trajectory is very close to the original trajectory. Moreover, The evaluation results also demonstrate the stability and feasibility of the proposed approach.