Thermoplastic vulcanizates (TPVs) of natural rubber (NR) and polypropylene (PP) (60:40) containing various dosages (0.5-5.5phr) of peroxide were prepared using a Haake Rheocord. The effects of peroxide content on the crosslink density, thermal behaviors, morphology, mechanical and rheological properties of NR/PP TPVs were studied. The crosslink density of TPVs increased with increasing of peroxide content. However, the tensile strength, tear strength and elongation at break obtained the maximum values when 2.5phr peroxide was added, which was ascribed to the presence of smallest particle size of crosslinked rubber phase at this peroxide content. It was proposed that the effect of DCP, which not only initiated crosslink reaction in NR phase, but also degraded the polypropylene molecules, played an important role in determined the morphology and properties of TPVs. The viscosity of TPVs decreased with shear stress, indicating pseudoplastic nature of the TPV samples. The elastic modulus of the samples gradually increases with the increase in DCP content.