The invention provides a method for preparing a porous TiO2 film. The method comprises the following steps: spinning a substrate with TiO2 slurry by using a uniform gel heating machine in the speed of 1800-2500r/s; drying for 0.5-1 hour at 60-80 DEG C; subsequently performing thermal treatment on the dried film layer, wherein in the thermal treatment, the annealing temperature is 420-550 DEG C, and the annealing time is 0.5-1 hours, so that the TiO2 film is obtained; the TiO2 slurry is prepared by grinding nano TiO2 powder and anhydrous acetic acid, subsequently adding deionized water and absolute ethyl alcohol, grinding respectively, and finally dropping an ethyl cellulose solution and terpilenol. The porous TiO2 film prepared by using the method is excellent in uniformity and compactness, relatively high in adhesion property with a glass substrate, good in long-lasting stability of the slurry, free of phenomena such as layering or agglomeration, simple in preparation method, low in cost and applicable to on-scale production.