The invention provides a metal Cu (I) complex, a preparation method and an application thereof. Tri-tert-butylphosphine imine anions and n-heterocyclic carbine are used as the ligands and coordinated with metal Cu (I) to synthesize the metal Cu (I) complex which can be used for catalyzing the boron hydrogenation reaction of alkyne. The metal Cu is cheap, the complex has relatively high solubility in a hydrocarbon solvent, the reaction conditions required by the catalytic reaction are mild, the reaction yield is relatively high, and the reaction has a specific regio-and stereo-selectivity. The catalyst is low in preparation cost and high in catalytic efficiency, and has a potential large-scale application prospect.