The present invention relates to a perovskite type composite soot combustion catalyst and a preparation method thereof. According to the preparation method, a La0.8Sr0.2Co1-xFexO3 precursor is prepared through a sol-gel method by using La(NO3)3-6H2O, Sr(NO3)2, Co(NO3)3-6H2O and FeCl3-6H2O as raw materials and using citric acid as a complexing agent, and the precursor is calcined to obtain a tail gas catalysis material La0.8Sr0.2Co1-xFexO3. According to the present invention, the site A and the site B of ABO3 are simultaneously and directly adjusted and changed, wherein the partial Sr<2+> is replaced with K<+>, and Fe<3+> and Co<3+> coexist at the site B, such that the La0.8Sr0.2Co1-xFexO3 perovskite material with characteristics of more defects, large specific surface area, uniform particle distribution and good catalytic effect is synthesized. According to the present invention, the product has advantages of uniform particle size, high catalytic efficiency, good high-temperature stability, wide raw material source and low raw material cost, and the preparation method has advantages of simple process, no requirement of large expensive equipment, convenient operation and low investment, and is suitable for industrial production.