The invention provides a carbon-aerogel-based supported organic amine CO2 absorbent. The carbon-aerogel-based supported organic amine CO2 absorbent adopts super-pore-volume carbon aerogel as a carrier, and organic amine with amino functional groups is uniformly supported in an aperture passage of carbon aerogel. A preparation method of the adsorbent comprises the following steps: mixing resorcinol, a formaldehyde solution, an alkali catalyst and distilled water to obtain a solution in which the total mass concentration of resorcinol and formaldehyde is 25-35%; fully ageing the solution at 50-90 DEG C to obtain an organic moisture gel; soaking the organic moisture gel in an acetone solution, displacing water in the organic moisture gel; performing supercritical drying by CO2; placing in a carbonization furnace for carbonization to obtain super-pore-volume carbon aerogel; uniformly mixing the super-pore-volume carbon aerogel and an organic amine solution, naturally cooling and further drying at 55-65 DEG C. The novel CO2 adsorbent with high adsorptive capacity is provided for CO2 adsorption and capture, the preparation process is simplified, the preparation cost is lowered, and the organic amine utilization efficiency is improved.