The invention provides a preparation method of a morphology-controllable indium nanocatalyst. The method concretely comprises the following steps: uniformly mixing a water-soluble indium metal precursor with an aqueous solution of a surfactant, introducing inert gas, adding a reducing agent, reacting for above 10min, cleaning, and drying to obtain the morphology-controllable indium nanocatalyst; and different carriers can be added in the synthesis process to realize in situ growth of the morphology-controllable indium nanocatalyst on a carrier. The method has the advantages of mild conditions, environmental protection, simple operation, low production cost and easy amplified synthesis. The morphology-controllable indium nanocatalyst prepared in the invention has a nanorod, nanorod cluster and nanorod-wire composite structure, and can be applied in the fields of NOx elimination, CO2 electrochemical reduction, water phase allylation of organic molecules, and alkaline battery hydrogen evolution and corrosion inhibition.