Belonging to the field of harm reducing and tar lowering of cigarettes, the invention relates to a strontium titanate nanotube, its preparation method and application. The strontium titanate nanotube can be used as an adsorbent to reduce the content of cigarette mainstream smoke nitrosamine. The preparation method provided in the invention includes: taking butyl titanate as a raw material, reacting it with alkali and ethanol, and subjecting the product and strontium chloride to a hydrothermal reaction, thus synthesizing strontium titanate with a high specific surface and a nanotube structure. The strontium titanate nanotube prepared in the invention can serve as an adsorbent to adsorb nitrosamine under room temperature. The strontium titanate nanotube can be made into particles and then added into cigarette filter sticks, thereby reducing the release of tobacco-specific nitrosamine in the mainstream smoke of cigarettes. The harm to smokers is reduced, and simultaneously the cigarette taste is not affected.