Chemical absorption using alkanolamine is the most used technique for carbon dioxide capture and storage (CCS). The energy required for regenerating the alkanolamine aqueous solution accounts for 70 - 80 % of the whole process. In this work, a new method was proposed to optimize the optimum ratio of mixed amines to reduce the regeneration heat. This method was developed base on slope analysing. The regeneration heat was characterized by absorption heat, sensible heat, and vaporization heat, which were calculated with the improved expression bases on expression reported by Nwaoha. The absorption heat, sensible heat, and vaporization heat of mixed amine with the wide range mass ratios of MDEA:MEA = 0:1, 0.2:0.8, 0.4:0.6, 0.6:0.4, 0.8:0.2, 1:0 were calculated. The results show that sensible heat is the main contribution of regeneration heat. Increasing the ratio of MDEA can reduce the sensible heat. The optimal mixed amine mass ratio is MDEA:MEA = 0.4:0.6, which has 34.51 % regeneration heat reduction compare with 30 wt.% MEA. The optimal ratio of mixed amine solution can reduce the regenerative heat to the greatest extent to reduce carbon emissions.