The invention relates to a palladium-based dopamine-coated magnetic carbon nano-tube catalyst and application thereof. A preparation method comprises the following steps: (1) oxidizing carbon nano-tubes to obtain carboxylic carbon nano-tubes; (2) dissolving a nickel salt in a mixed solution of ethyl alcohol and water, adding the carboxylic carbon nano-tubes, performing ultrasonic treatment, drying and roasting to obtain nickel-filled carboxylic carbon nano-tubes; (3) dispersing the nickel-filled carboxylic carbon nano-tubes in Tris buffering liquid, adding dopamine, stirring, and performing centrifugal drying to obtain poly-dopamine-coated magnetic carbon nano-tubes; and (4) dispersing the poly-dopamine-coated magnetic carbon nano-tubes in an aqueous solution of a palladium salt, performing ultrasonic treatment, heating, stirring, evaporating, drying, and reducing to obtain the palladium-based dopamine-coated magnetic carbon nano-tube catalyst. The palladium-based dopamine-coated magnetic carbon nano-tube catalyst has excellent magnetic separating performance and can be effectively separated from a liquid phase after the completion of a reaction; and the recycling rate of the catalyst is effectively improved.