The invention provides impact resistant copolymerized polypropylene and a preparation method thereof. The preparation method of the impact resistant copolymerized polypropylene includes the steps: adding a main catalyst, a cocatalyst and a modifier into a first gas-phase reactor, introducing propylene and hydrogen into the first gas-phase reactor, and carrying out a first polymerization reaction to obtain a first reaction product; collecting a solid part of the first reaction product, adding the solid part of the first reaction product into a second gas-phase reactor, and introducing ethylene,propylene and hydrogen into the second gas-phase reactor, carrying out a second polymerization reaction, and collecting a solid part of the second reaction product, to prepare the impact resistant copolymerized polypropylene. The activity of the main catalyst is 10000-20000 g/g. The preparation method can ensure the long-term stable production of the impact resistant copolymerized polypropylene,the impact strength of a simply supported beam of the impact resistant copolymerized polypropylene is more than or equal to 45 kJ/m<2>, the melt index is 14-19 g/10 min, and the odor grade is less than or equal to 3. The impact resistant copolymerized polypropylene with high impact resistance, middle melt index and low odor is prepared.