Electrical capacitance tomography (ECT) is a technique developed in recent years, which aims to measure multi-phase flow. The quality of reconstructed images is the bottleneck for its successful applications. Sensitivity matrix is calculated based on the known permittivity distributions, which is necessary in the most common used sensitivity-based image reconstruction algorithms of ECT. It is assumed that sensitivity matrix will hardly be affected by flow regimes. As a result, the fixed sensitivity matrix was used during the image reconstruction. However, there exists ‘soft-field’ effect and the sensitivity matrixes are changeable corresponding to different flow regimes, which results the decrease of reconstructed image quality. Therefore, Landweber iterative algorithm with updated sensitivity matrix was studied in this paper to improve the quality of reconstructed images. The initial image for sensitivity matrix update was obtained by Landweber iterative algorithm, and the results of different sensitivity matrix update intervals were compared. The times of sensitivity matrix updating were also analyzed. Experimental and simulation results showed that reconstructed images with higher accuracy can be obtained.