Abstract: Combined effect of sodium 2,2'-methylene-bis-(4, 6-di-tert-butyphenyl) phosphate (NA-11) and sodium bicycle2, 2, 1-heptane-2, 3-dicarboxylate (NA-CA) on mechanical properties and crystallization behaviors of isotactic polypropylene (iPP) were investigated. The nucleating agents and iPP were blended using a twin-screw extruder to prepare NA-11/NA-CA/iPP composites. The mechanical properties, crystallization behaviors and microstructure were characterized by universal material testing machine, XRD, DSC and polarized optical microscopy (PLM). The results show that NA-11 and NA-CA nucleating agents combined can improve the tensile properties and the flexural properties of iPP. The combined nucleating agent induces the formation of α phase iPP. The crystallization peak temperature increases by 20.3 ℃ and the crystallinity increases by 8.8% when 0.4wt% 1:1 combined nucleating agents are added into iPP. PLM show that the combined nucleating agents make the spherulite size of iPP decrease obviously. NA-11 and NA-CA combined nucleating agents show good nucleating efficiency and two nucleating agents show synergistic effects on improving crystallization behaviors and mechanical properties of iPP.