Melt vibration technology was used to prepare injection sample of HDPE/nano-CaCO3 blend, whose mechanical properties were improved significantly. Compared with conventional injection molding, the enhancements of the tensile strength and impact strength of the sample molded by vibration injection molding were 41.2 and 43.2%, respectively. According to the SEM, WAXD, and DSC measurement, it was found that a much better dispersion of nano-CaCO3 in sample was achieved by vibration injection molding. Moreover, crystal orientation degree of matrix HDPE increased under the effect of melt vibration. The crystallinity degree of HDPE in vibration sample increased by 5.5% compared with conventional one. The improvement of mechanical properties of HDPE/nano-CaCO3 blend prepared by low-frequency vibration injection molding attributes to the even distribution of nano-CaCO3 particles and the orientation of HDPE crystals and increase of crystallinity degree under the influence of melt vibration.