The invention discloses a green catalyst-free method for preparing gallium nitride nanowires, and belongs to the field of preparation and growth method of inorganic compound semiconductor materials. Aone-dimensional linear GaN nanostructure with excellent performance is prepared by a plasma enhanced chemical vapor deposition (PECVD) system, under a condition without any catalyst and with green and pollution-free N2 as a nitrogen source. The method has the advantages of low cost and simple process, and takes polished graphite as a substrate and metal gallium and carbon powder as precursors. Inthe PECVD system, the reaction pressure is adjusted to 30 Pa-50 Pa; the reaction temperature is 825 DEG C-875 DEG C; the flow velocity of N2 is 10-40 cm<3>/min; the flow velocity of H2 is 5-10 cm<3>/min; the power of a radio frequency power source is 80 W-120 W, and the reaction is performed for 1-3 h to obtain a product. The product is the one-dimensional GaN nanowires having a hexagonal wurtzite structure and has typical violet luminescence characteristics and excellent field emission properties.