This study proposes a high-resolution reconstruction algorithm for off-axis digital holography based on Kronecker convolution-derived spectrum fusion to address the issue of severe interference from zero-order spectra during phase recovery. In this process, first, Kronecker convolution was performed on the off-axis digital hologram and a 2×2 constant matrix. Thereafter, two-dimensional Fourier transform was applied to the convolved hologram, producing a spectrogram containing the original and derived spectra. Depending on the interference level of the zero-order spectrum, bandpass filters of varying sizes were employed to select multilevel-derived spectra, followed by numerical reconstruction. Finally, image fusion technology was used to combine the multiple reconstruction results to produce high-resolution images. Compared with existing off-axis digital holographic reconstruction algorithms, the proposed algorithm reduces interference caused by zero-order spectra. It achieves this without increasing the complexity of off-axis digital holographic structures. This facilitates the retrieval of more object information and allows for high-resolution phase reconstruction. Experimental results show that the proposed algorithm simplifies calculations, significantly diminishes the influence of zero-order spectra on effective spectral information, and achieves high-resolution reconstruction in off-axis digital holography.