In this paper, pyramid-structured silicon wafers were etched in a reactive ion etching system at room temperature and without any negative voltage pulses to obtain antireflective nanostructures. The effects of the etching time, etching power and the flow ratio of the SF 6 and O 2 (F SF6 /F O2 ) on the morphologies and reflective properties of the etched samples were studied. Scanning electron microscope was used to investigate the morphologies of etched samples. The surface reflectance measurements were carried out using UV–vis-NIR spectrophotometer. A reflectance of 4.72% from the etched surface in the wavelength range of 400–800nm was obtained under etching time of 20min, etching power of 150W and F SF6 /F O2 of 18sccm/6sccm. Meanwhile, samples etched with F O2 lower than 6sccm can’t get low reflective silicon structure. Besides, the results show that overlong etching time of 30min and too big etching power of 225W would make the nanostructures too sparse to obtain a low reflectance.