With TEM, XRD, FT-IR, and the physical gas adsorption techniques, porous properties of nano-fibriform silica (MLD: 92.73%) from natural chrysotile were studied. The results indicate that nano-fibriform silica is porous and that the nano-fibriform structure is attributed to the complete dissolution of the brucite octahedral sheets of chrysotile and the collapse of some Si-O tetrahedral sheets. Its length is at the micron or nanometer scale. There are two types of pores: cumulate pores and pores on the nanofibre. The latter pores, whose apertures are less than 5 nm, consist of pores among the particulate SiO_2, pores among the aggregates of particulate SiO_2, remnant nano-tunnels and capillaries. These pores belong to mesopores whose apertures are mainly of 2.1 and 3.8 nm. As the carrier of catalyzer and the filler to reinforce rubber and plastics, nano-fibriform silica shows better performance than traditional silica.