The invention discloses a high-performance adsorption material and a preparation method thereof. A hierarchical-pore nitrogen doped carbon/MgO composite microsphere material is prepared by performing a high-temperature thermal treatment carbonization method on polyimide serving as a carbon and nitrogen source, polyurethane foam serving as a macroporous scaffold and metal magnesium salt serving as an additive. According to the high-performance adsorption material and the preparation method thereof, the use of an expensive template agent and a toxic raw material reagent is avoided; the prepared composite microsphere material has an ideal flower-shaped spherical appearance, is of a hierarchical-pore structure with micro holes and macro holes, has controllable surface characteristics, excellent structural stability, high nitrogen content and magnesium content, and shows high adsorption volume and excellent circulating stability when used as a CO2 adsorption material. The preparation method disclosed by the invention is simple and feasible; the process is controllable, and the reaction time is short; furthermore, no complicated experimental equipment and complicated experimental steps are needed; and the industrial large-scale production is facilitated.