【Objective】The ecotoxicity of microplastics (MPs) to soil fauna is widely recognized. However, the degree of MP aging under different exposure durations, their differential toxic effects on soil fauna, and the dynamics of toxicity changes remain poorly understood.【Methods】In our study, microcosm experiments were conducted to compare both the aging degree of polyethylene (PE-MP) and polylactic acid microplastics (PLA-MP) exposed for 30/60 days and their ecotoxicities to earthworms. 【Result】The characteristic peak intensity of both aged PE-MP and PLA-MP exhibited significant alterations at 717 cm?1 and within the 1000-1257 cm?1 range. The carbonyl index (CI) of PE-MP and PLA-MP increased from 0.26 to 0.72 and 3.23 to 3.35, respectively. Also, scanning electron microscopy (SEM) demonstrated visible surface cracks and fractures, confirming aging on both MPs. Aging significantly enhanced the toxicity of MP on earthworms and the redox balance of earthworms was disrupted when exposed to both PE-MP and PLA-MP. This was associated with fluctuations in reactive oxygen species (ROS) and oxidative stress. After 60 days of exposure, the concentration of malondialdehyde (MDA) increased by 36.22% and 11.47%, while glutathione-S-transferase (GST) increased by 107.32% and 33.44% in PE-MP and PLA-MP treatments, respectively. In addition, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) decreased by 27.07% & 30.62%, 24.78% & 55.51%, and 52.90% & 47.78%, respectively. SEM and histopathological analyses revealed more severe damage to the epidermis and intestinal tissues in PLA-MP-exposed earthworms than those of PE-MP. Intestinal MP bioaccumulation significantly increased from 2.50±0.28 μg·mg–1 to 6.17±0.13 μg·mg–1 with prolonged exposure, ultimately causing irreversible physiological impairment. 【Conclusion】The aging of PE-MP and PLA-MP in soil induced significant physiological damage and oxidative stress in Eisenia fetida. Notably, PLA-MP shows greater susceptibility to aging and induces stronger physiological toxicity compared to PE-MP.