The invention discloses a 
reaction system for preparing 
stress whitening resistant 
polypropylene and a method for preparing 
polypropylene by employing the 
system. A liquid-phase stirring reactor is sequentially connected with a gas-phase 
fluidized bed flashing reactor and at least two gas-phase 
fluidized bed reactors which are connected in series. According to the method, 
polypropylene granules are sequentially subjected to propylene liquid-phase homopolymerization, propylene gas-phase homopolymerization, propylene 
ethylene gas-phase copolymerization and 
ethylene gas-phase spontaneous 
polymerization through the 
reaction system and a Ziegler-
Natta catalytic 
system, and pass a gas-
solid drying and separating 
system and are discharged, so that the 
stress whitening resistant polypropylene is obtained. The system has the advantages that a copolymerization reactor is additionally arranged at the stage of gas-phase 
polymerization, a flow of propylene liquid-phase homopolymerization, propylene gas-phase homopolymerization, propylene 
ethylene gas-phase copolymerization and ethylene gas-phase spontaneous 
polymerization is formed, a notable characteristic is reflected in the stage of gas-phase polymerization, 
polymer granules are subjected to three polymerization stages including propylene homopolymerization, propylene ethylene copolymerization and ethylene spontaneous polymerization, and the interface integration of different structural molecules is properly improved, so that the 
stress whitening resistant polypropylene has relatively good 
mechanical property and 
processing property, and the 
reaction system further has outstanding characteristics that the 
occurrence probability of stress 
cracking is reduced, and the stress whitening phenomenon of products is obviously improved.