In consideration of the crosstalk between reconstructed image and zero-order image existed in the digital reconstruction for off-axis digital holography, this paper presents a method to suppress the zero-order image. Based on the principle that the pixel gray-scale of the image is decided both by the image illumination and surface reflectance, the hologram is considered as a product of the incident and reflected components. The incident components which change slowly are mainly concentrated in the low-frequency region, and the reflected components which determine the detail of the image are concentrated in the high-frequency region. A reasonable homomorphic filter with the upper and lower limits of 0.001 and 1 respectively and a diameter of 300 pixel is designed and processed into the hologram. The results show that the zero-order image can be suppressed with only one Fresnel digital hologram at a distance of 34 cm. Meanwhile, the contrast and the details of reconstructed image at the same distance are improved.