The invention belongs to the field of environment purifying functional materials, and particularly relates to a method for preparing a titanium-germanium molecular sieve. The method comprises the following steps: preparing a titanium-germanium organic solution, namely heating and refluxing absolute ethyl alcohol, n-butyl alcohol, tetrabutyl titanate, tetramethylgermanium, cetyl dimethyl amine oxide and ethylenediamine tetraacetic acid, adding OP-10 and Tween-60, heating and refluxing, adding a hydrochloric acid solution, and heating and refluxing; performing thermosynthesis, namely reacting the titanium-germanium organic solution in a stainless steel autoclave, filtering, washing and drying to obtain solid powder A; performing channel activation, namely heating and refluxing the solid powder A in a phosphoric acid solution, filtering, washing and drying to obtain solid powder B; calcining the solid powder, and grinding to obtain the titanium-germanium molecular sieve. The molecular sieve can spontaneously decompose organic molecules in the light, and is applicable to purification treatment of organic pollutants in atmosphere and water environment.