Abstract: The effect of oxidation induction time on the aging characteristics of high-density polyethylene (PE-HD) induced by artificial thermo-oxidation aging at 100 °C was studied in this work. Furthermore, we compared and analyzed the variation of mechanical properties including tensile strength, impact strength and elongation at break at different aging time, and also investigated the variation of crystallinity and oxidation induction time of HDPE in different periods of induction during artificial thermo-oxidation aging. The results indicated the crosslinking between molecule chains played a key role in the initial stage of thermo-oxidation aging, but the chain breaking and degradation were predominant in the latter stage. The longer oxidative induction time for HDPE led to better resistance to thermo-oxidation aging during the thermo-oxidation aging process at 100 °C. Oxidation induction time can be adopted as a relative indicator for the evaluation of HDPE oxidation stability.