Aiming at this threshold selection problem for multi-current projection fusion, a method based on dynamic time warping was proposed. Firstly, the sequences of gray value-effective edge gradient is calculated from the projections with different currents. Secondly the dynamic time warping distance is used to match the similarity of the above sequences, and the optimal fusion threshold is automatically determined. Finally the sub regions are extracted for fusion based on the threshold, achieving a higher dynamic range of the detector. The average error of fusion threshold at each angle is only 2.26% calculated by the proposed method, which could avoid subjectivity in the fusion threshold selection. Simulation and experimental results show that both the SNR and the measurement accuracy of geometric dimensions based on the fused computed tomography image are better than those with a fixed threshold.