A process for preparing a titanic acid salt, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure, wherein the process includes the steps of: preparing a titanium-containing peroxo-complex solution; adding a basic metal compound to the titanium-containing peroxo-complex solution to form a mixture solution; adding one of polyvinyl alcohol, hydroxypropyl methyl cellulose, and polyethylene glycol to the mixture solution to form a precursor dispersion; and subjecting the precursor dispersion to a solvothermal reaction to obtain the titanic acid salt having a hierarchical structure. The process for preparing a titanic acid salt, titanic acid, and titanium oxide having a controllable particle size and a hierarchical structure, can not only realize the regulation of morphology and particle diameter of constituent units in the hierarchical structure, but also can achieve the regulation of particle size in the hierarchical structure.