In order to study the performance of Indonesian oil sand tailings/polyethylene (HDPE) composites, scanning electron microscopy (SEM) and X⁃ray fluorescence spectrometry (XRF) were used to obtain the morphology, size and main component calcium carbonate (CaCO3), the main component of oil⁃sand tailings before and after modification, which is about 77.170%. And the surface was dried with different mass fractions of stearic acid, the best modifier content is 5%; the mechanical properties of oil sand tailings/HDPE composites were characterized by impact strength, tensile strength, elastic modulus and differential scanning calorimetry (DSC). The results show that with the increase of tailings filling, the oil sand tailings have obvious strengthening and toughening effect on HDPE. When the tailing sand content is 50%, the toughening effect is best. However, a large amount of oil sand tailings is distributed in HDPE to increase the defects in the matrix, and causes stress concentration phenomenon when subjected to external force, which results in the decrease of tensile strength. The crystallization property study shows that the addition of oil sand tailings has heterogeneous nucleation effect on polyethylene and enhances the toughness of composites.