The invention discloses multi-defect multi-doped titanium oxide nanoparticles with high visible-light catalytic activity and a preparation method of the titanium oxide nanoparticles. The titanium oxide has the size of 10-20nm, the particle size of 10-20nm and the specific surface area of 140-160cm<3>, and the particles refer to truncated octahedron nanoparticles coexisting on surfaces {001} and {101}. The preparation method comprises the following steps: respectively taking tetrabutyl titanate and ammonium hexafluorotitanate as a titanium source and a fluorine source, synthesizing a mixture of TiO2 and NH4TiOF3 by using a hydrothermal method, further treating the prepared sample by using boric acid, enabling the NH4TiOF3 to be subjected to topological transformation so as to be transformed into the titanium oxide, and in-situ doping of a small amount of nitrogen is realized so as to obtain the titanium oxide exposed on the {001} crystal face. Lots of vacancy is introduced into the surface of the titanium oxide by adopting a photo-reduction method, and fluorine doping is realized. According to oxygen vacancy introduced into the invention, the absorption of the titanium oxide on visible light can be obviously improved, and due to exposure of the {001} crystal face and co-doping of nitrogen-fluorine atoms, separation of carriers in the photocatalysis process is improved. Therefore, rhodamine B can be efficiently degraded under visible light radiation.