The invention discloses a preparation method of a nano platinum/titanium dioxide nanotube array composite material. According to the method, a titanium dioxide nanotube array is prepared on the surface of a titanium sheet through the anodic oxidation process. The method comprises the following steps of: dipping the titanium sheet containing the titanium dioxide nanotube array on the surface into aqueous alkali, and then dipping into an acid solution to obtain the titanium sheet with an activated titanium dioxide nanotube array on the surface; dipping the titanium sheet with the activated titanium dioxide nanotube array on the surface into a Pt(NH<3>)4Cl2 solution to obtain a precursor of the nano platinum/titanium dioxide nanotube array composite material; and performing reduction reaction to the obtained precursor of the nano platinum/titanium dioxide nanotube array composite material through a NaBH4 solution, thus obtaining the nano platinum/titanium dioxide nanotube array composite material. According to the nano platinum/titanium dioxide nanotube array composite material prepared by the method, the loaded platinum nanoparticles are small in size, high in loading capacity and uniform in distribution; and the preparation method is simple, mild in reaction condition, low in cost, and applicable to industrial application.