To investigate the cracking failure mechanism of Nitrile Rubber 5080 （NBR 5080） seals and propose effective preventive measures， this article performed failure analysis and accelerated aging tests ，including air exposure， stress loading， effects of tensile strain， and a comparison between soft and hard NBR 5080 raw materials. The results indicate that the aging and cracking of the sealing rings are caused by the combined effects of ozone in the air and sustained stress. Both the air environment and tensile stress contribute to the aging of the sealing rings， while the actual working tensile strain exceeds the optimal range， with excessive tensile strain significantly exacerbating stress concentration. For soft NBR 5080 sealing rings exposed to air under a tensile strain of 1.096%， stress-induced aging is the dominant factor leading to cracking. In contrast， for hard NBR 5080 sealing rings， the influence of stress-induced aging is relatively minor.