Aiming at the zero-order image's effect on the quality of reconstructed images in digital holography, by analysis of spectrum characteristic as well as recording and reconstruction theory, a method of zero-order image elimination in digital holography by using of finite impulse response (FIR) filter is proposed. The method is based on only one hologram and the digital image processing for preprocessing the digital hologram in spatial domain to eliminate the zero-order image, free of phase modulator or any other extra-equipment. The comparison of elimination zero-order image in reconstructed hologram before and after using FIR filter in digital simulation and experiment presents that this method can eliminate the zero-order image and enhance the quality of reconstructed image with a simple algorithm.