The invention relates to a denitration and purification method of catalytic cracking regenerated flue gas. Two catalyst bed layers are filled in a constant-temperature section of a reactor, the first catalyst bed layer is arranged at the upper section, the second catalyst bed layer is arranged at the lower section, no partition layer is arranged between the two catalyst bed layers, and catalytic cracking regenerated flue gas enters the catalyst bed layers of the reactor from the bottom of the reactor and then is heated to come into reaction; the mass ratio of a first catalyst to a second catalyst is 1:1-10; the first catalyst consists of nano CeO2 and perovskite composite oxides loaded on nano CeO2, the second catalyst is a molecular sieve with a transition metal doped skeleton, and the second catalyst contains aids; the load of the perovskite composite oxides on nano CeO2 is 10-50wt%; the molar ratio of the transition metal to the aids is 0.1-0.3; and the silicon-aluminum molar ratio of the HZSM 5 molecular sieve is 25-100, and the load of the transition metal on the molecular sieve is 0.05-6wt%. The method can efficiently reduce nitric oxides and has good stability and causes no secondary pollution.