Nature provides various exquisite photonic structures of antireflection. Here, we investigate the color and structure of the inner surface of the shell edge (ISSE) of blue mussel shells, using a fiber optical spectrometer, scanning electron microscope (SEM), and X-ray diffraction (XRD). We demonstrate that the structurally assisted black color of the ISSE is produced by a pyramidal microstructure. Furthermore, we use the two-step biotemplate (TSBT) method to successfully replicate this microstructure. Particularly, we modify this method by using a poly(vinyl alcohol) (PVA) film as the negative replica and an epoxy resin film as the positive replica both fabricated without vacuum treatment. We show that the natural and replicated structures show a reflectivity of ∼4% and of ∼3% in the visible wavelength. Finally, we hope our investigation can provide basic data for the study of the bioinspired antireflective structures, which have a promising application in smart windows and optical devices.