According to the monatomic copper/boron double-site multifunctional catalyst and the preparation method and application thereof, copper salt serves as a metal source, a cyanamide compound serves as a nitrogen source, organic acid serves as a dissolving agent of chitosan, soluble boron salt serves as a boron source, chitosan serves as a carbon source, silicon dioxide and frozen ice serve as double templates, a pyrolysis-etching-activation strategy is adopted, and the monatomic copper/boron double-site multifunctional catalyst is prepared. And the copper/boron double-site catalyst material with the hierarchical porous structure is successfully prepared. The catalyst has a hierarchical porous structure, provides abundant mass transfer channels for catalytic reaction, and further realizes efficient catalytic performance. In addition, the catalyst can also be used for reducing carbon dioxide to prepare synthesis gas. Compared with the prior art, the method for preparing the monatomic copper/boron double-site multifunctional catalyst material is simple, reliable, low in production cost, short in process, low in equipment requirement, easy to amplify experiments and capable of achieving industrial large-scale production.