The invention discloses preparation and usage methods of a high-temperature CO2 modified calcium-based adsorbent and a preparation method of a calcium-based CO2 adsorbent. Oil sand pyrolysis residues are selected as a main calcium source and is modified through the processes such as oil sand pyrolysis residue and kaolinite mixing and compounding, high-temperature calcination and ethanol solution hardening and tempering for forming to obtain a modified calcium-based CO2 adsorbent; the modified calcium-based CO2 adsorbent is large in adsorption capacity and has the good effect of removing CO2 in high-temperature flue gas of a thermal power plant and high cyclic adsorption stability, and the high-temperature CO2 adsorption removal rate after 25 times of cyclic regeneration is still kept to 65% or above. The preparation method has the advantages that the calcium source is the oil sand pyrolysis residues, and the preparation process is simple, quick and convenient to operate, low in cost and friendly to the environment and is used for adsorption and separation of high-temperature gas CO2; the CO2 in the flue gas can be directly adsorbed, and the advance influence of carbon emission on the environment and climate is reduced; the purpose of using waste to treat waste can be achieved, the methods conform to low-carbon green economy, and the effect is obviously improved compared with other calcium-based CO2 adsorbents.