As the magnification chrometism caused from different wavelengths of color lasers in the optoelectric reconstruction based on a spatial light modulator effects on the quality of reconstructed images,this paper focuses on the reason that the magnification chromatism arises.In order to remove the magnification chromatism, it proposes a method to sample the three color objects with disparity in the process of hologram computing to improve the image quality. A full color electro-holographic system based on a time shearing method is established and holograms computed by the Iterative Fourier Transform Algorithm (IFTA) are reconstructed. The experiment indicates that the magnification chromatism 33.6% for red and 12.5% for blue can be both removed,which shows that the method proposed is verified by experiment results.