Voice transformation is an important issue in speech synthesis when we need to synthesize multiple output voices but do not want to rebuid the synthesis system. Speech transformed by the conventional method using Gaussian Mixture Model (GMM) is not high-quality due to the oversmoothness of GMM. Therefore, a number of methods have been proposed to overcome the disadvantages of the conventional method using GMM. Among them, Hidden Markov Model Trajectory Tiling (HTT) and Temporal Decomposition – GMM (TD-GMM) improve the effectiveness of voice transformation. However, they still have drawbacks. In this paper, a voice transformation method using the modified restricted TD (MRTD) is proposed. The experimental results with Vietnamese and English corpus confirm the effectiveness of the proposed method compared with HTT and TD-GMM.