Abstract: The injection molding processing of recycled polypropylene(PP) was studied by orthogonal experiment.Recycled PP was injected with ethylene-octene copolymer(POE) modified by maleic anhydride and modified POE/nano-CaCO3 as toughening agent.The influences of toughness agents on the microstructure and mechanical properties were tested.The results show that the influencing factors of the mechanical properties could be ranked in an order from the greatest to the smallest such as injection temperature,injection pressure,holding pressure,holding time.The best injection molding parameters were as fallows: injection temperature 220 ℃,injection pressure 70 MPa,holding pressure 55 MPa,holding time 40 s.It was found that the tougheness had been greatly improved by using modified POE and modified POE/nano-CaCO3 as toughening agents,and the best addition quantities were both 25%.The samples with modified POE/nano-CaCO3 had better toughness.