The invention discloses a preparation method of a titanium dioxide photocatalyst. The preparation method comprises the following steps of: firstly, putting a Ti-Cu amorphous alloy strip into a sealed container containing a nitric acid solution with the mass percent of 65%; adding NaF and citric acid; keeping the heat of the sealed container at 60 DEG C to 80 DEG C for 36h-72h, and taking out the sealed container; and finally, sintering obtained substances at 450 DEG C to 550 DEG C for 1h-2h to obtain the titanium dioxide photocatalyst. The titanium dioxide prepared by the invention is anatase type titanium dioxide with a porous hexagonal prism shape and is the titanium dioxide with a good photo-catalytic performance. The preparation method provided by the invention is simple to operate and a reaction process is easy to control; the obtained titanium dioxide has excellent performances and the preparation method is an efficient and economical preparation method.