The invention provides a method for preparing tenofovir. The method is characterized by comprising the following steps: 1) reacting 9-(2-hydroxy propyl) adenine with a compound as shown in the formula (1) in the specification in the presence of magnesium alkoxide to prepare tenofovir ethyl ester, wherein Y is selected from methyl, trifluoromethyl, phenyl or 4-trifluoromethylphenyl; 2) hydrolyzing the tenofovir ethyl ester in the presence of a dealkylation reagent to prepare tenofovir. The method for preparing tenofovir provided by the invention has the advantages of safe process, good product quality, high yield and suitability for industrialization.