The invention discloses a supported flower-shaped hierarchical-structure nanoscale precious metal material and a preparation method thereof. The method comprises the following steps that firstly, heteropolyacid and dopamine are co-assembled by adopting a chemical self-assembling method so as to obtain the flower-shaped hierarchical structure material assembled by the heteropolyacid and the dopamine; and then the flower-shaped hierarchical structure material is dispersed into a soluble salt aqueous solution of precious metal, pyrocatechol groups of the flower-shaped hierarchical nano-structureis used for reducing precious metal ions in situ so as to prepare the supported flower-shaped hierarchical-structure nanoscale precious metal material. The preparation method has the advantages of being simple and convenient to operate and controllable in height. The prepared supported flower-shaped hierarchical-structure nanoscale precious metal material is a crystal material with a face-centeredcubic structure, is controllable in size and morphology and has a wide application prospect.