Abstract: In this paper, PP/nano-TiO2 composites were prepared via melt blending, the properties of the composites were analyzed by means of mechanical tests, infrared spectroscopy, POM, SEM, and TEM, and then the influence of microwave irradiation on the properties of PP/nano-TiO2 composites was studied. It showed that after the PP master-batch was irradiated by microwave, the elongation at break greatly improved without decreasing the tensile and yield strengths, the degree of crystallinity increased by nearly 20 %, the crystal grain size increased, and crystallization rate had no changes. Infrared spectrum showed that some polar groups were brought into PP/nano-TiO2 composite; thereby the compatibility between the two-phases was improved, which was considered the reason for the improvement of the properties.