Abstract: The present invention relates to a method for preparing self-assembled silicon nanotubes (SiNTs) by a hydrothermal method. A method for preparing self-assembled SiNTs comprises forming a mixture of silicon oxide and water in a sealed container, wherein the mixture has a silicon oxide to water ratio of no more than 10% by weight. The mixture is maintained at a constant temperature and a constant pressure, and the mixture is stirred for a period of time. Self-assembled SiNTs may be formed with an average inner diameter of less than 5 nm and an average outer diameter of around 15 nm. The present invention completely utilizes non-toxic raw materials, and the materials and process do not pollute the environment, so the method satisfies the development trends of the modern industry.