Nanoporous silicon powder was prepared by chemical etching method using silicon powder with purity of over 99% and particle size of smaller than 20 μm as raw material and HF, HNO₃, distilled water and sodium nitrite as the etching medium The nanoporous silicon powder were characterized by scanning electron microscope(SEM), specific surface tester and Fourier transform infrared spectrum(FTIR). The porous silicon (PSi)/sodium perchlorate composite materials were prepared and their combustion test was performed. Results show that the main factor affecting the pore-size distribution is nitric acid concentration in the etching system. The etching time is the key factor increasing the specific surface area of nanoporous silicon powder. The best etching conditions are nitric acid concentration of 5.2% and etching time of 120 min. The prepared nanoporous silicon powder is nanoporous materials, whose surface is covered by large amounts of Si-H bonds and the surface area is up to 58.2264 m²·g^-1 . The prepared PSi/sodium perchlorate can combust violently, accompanied with deflagration phenomenon and can be used as green ignition reagent or combustion agent.