A process of forming silicon-based nanowires heats high-surface-oxygen-content silicon powders to initiate vapor-solid reaction to form nanowires. The reaction gas is charged to react with the Si powders to form the silicon-based nanowires such as silicon nanowires or SiC nanowires. With control of the reaction gas, the components of the nanowires can be exactly controlled without the addition of metallic catalysts. Thereby, the nanowires can be made with reduced cost.