For the problem of the impact resistance in the application of PP (polypropylene) , the ground rubber tire (GRT) is used for modification so that the PP could be toughened. The impacts on mechanical property GRT/PP blending with unequal contents and particle sizes of GRT are focused and reserched. The result shows that the flexural strength and tensile strength of the blending decreases, the izod notched impact strength of blending improves and then decreases while the izod notched impact strength reaches the peak when the amount of the added GRT is 15%. In addition, neither the overly large particle size nor the overly tiny particle size makes a good result. The blending is of the best overall performance when the particle size of GRT is 80 mesh and with the amount of the added GRT of 15%.