A method for preparing a nano-titanate, a nano-titanic acid and a nano-TiO2 containing embedded A nanoparticles is provided respectively. In this method, a Ti-T alloy with a A-group element solidly dissolved therein is used as a titanium source, and reacted with an alkali solution under a certain condition. In combination with subsequent treatment, the preparation of a titanate nanotube, a titanic acid nanotube, and a TiO2 nanotube/rod containing embedded A nanoparticles, respectively, is further achieved with high efficiency and low cost. Moreover, a method for preparing metal nanoparticles is also provided by removing the matrix of the composites. The present preparation methods is characterized by simple process, easy operation, high efficiency, low cost. The product is of promising application in polymer-based nanocomposites, ceramic materials, catalytic materials, photocatalytic materials, hydrophobic materials, effluent degrading materials, bactericidal coatings, anticorrosive coatings, marine coatings.