A new method of strengthening and toughening HDPE was studied. Two typical inorganic particles, talc and CaCO3 were used as fillers to HDPE matrix, and the co-composite effects of inorganic particles were investigated. The results indicated that the co-composite method has advantages in several aspects: in virtue of the strengthening effect of active particles, the sharply decreasing tendency of material toughness induced by the weak interface along inactive particles and the matrix could be effectively amended, the strength and toughness of the co-composite materials could be simultaneously controlled at a higher level by combining the characteristics of two different inorganic particles.