The invention relates to a quality-divided and graded utilization method and system of coal-burning supercritical carbon dioxide power generation flue gas energy and working medium energy. The quality-divided and graded utilization method and system of coal-burning supercritical carbon dioxide power generation flue gas energy and working medium energy have the benefits as follows: firstly, high-grade flue gas energy and working medium energy multistage reheat expansion measures are utilized, so that a isothermal heat absorbing process being close to the temperature of a high temperature heat source is realized, the average heat absorbing temperature is improved, and the circulating efficiency of the system is improved; secondly, middle-grade flue gas energy and working medium energy coupling, graded dividing and backheating measures are utilized, the energies of the flue gas and working medium in a medium temperature zone are fully utilized in a graded manner, the heat transfer temperature difference of cold and heat fluids are reduced as far as possible, the irreversible loss of available energy due to large temperature difference is reduced, and both the heat exchange efficiency and circulating efficiency are improved; thirdly, a low-grade flue gas energy and working medium energy graded heating cold air and fuel system is utilized, the low temperature exhaust heat of flue gas and working medium is utilized, the heat of flue gas and working medium released to the environment is reduced, a isothermal heat releasing process being close to the environment temperature is realized, the cold end loss is reduced, and the circulating efficiency is improved.