Abstract: In order to improve the image reconstruction quality of electrical capacitance tomography (ECT), a dimension reduction based Tikhonov regularization image reconstruction algorithm was proposed. First, an initial reconstruction image was obtained by the Tikhonov regularization algorithm, and then the gray values of the pixels in the reconstructed background region were regarded as known quantities "0" and were removed from the gray value vector to be calculated. By the dimension reduction, the ill-posedness of ECT inverse problem was alleviated. The simulation and experimental results show that the proposed algorithm has higher reconstruction accuracy and its reconstructed images are closer to the true distributions compared with the Landweber iteration algorithm and the Tikhonov regularization algorithm. Thus, this paper provided a new idea for ECT image reconstruction.