A slow calcination process was introduced to get silica adsorbents with hierarchically nano-porous from rice straw and the adsorbents was tested for the removal of heavy metal ions. The obtained fibers were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric (TG) analysis, respectively. A possible formaiton mechanism of the obtained silica fibers was suggested. By introducing active sites on their backbones, these silica fibers showed great capability in removing Cu2+, Ni2+, Cd2+ and Pb2+ from aqueous solution via adsorption with a removal efficiency of 99%. The adsorption equilibrium was reached within only 10 mins, suggesting that the introduced active sites were readily available and easily accessible. In view of recycling of resources and practical operations, such silica fibers with active sites hold great promise in removal of heavy-metal ions via effective adsorption process.