The invention discloses a preparation method and application of a TiO2 nanotube coated with an amorphous layer. According to the preparation method, titanium oxide powder is firstly adopted and subjected to hydrothermal reaction in a sodium hydroxide solution to obtain a sodium titanate nanotube; the sodium titanate nanotube is washed and subjected to acid exchange to obtain a titanic acid nanotube; lastly, the titanic acid nanotube is subjected to annealing at a proper temperature to obtain the titanium dioxide coated with the amorphous layer. The main body of the titanium dioxide nanotube is an anatase phase and adopts a one-dimensional tubular structure; a part of amorphous titanium dioxide remains on the surface of main body of the titanium dioxide nanotube. As the amorphous titanium dioxide layer is adopted, the specific surface area of the material is higher and the surface functional groups are rich; moreover, the material has certain light absorbing characteristics in a visible light region and the TiO2 nanotube can be applied in the field of water treatment, sensing, dye stuff/ quantum dot sensitization solar batteries.