Abstract: Probiotics are thought to slow aging and extend lifespan, yet their exact molecular mechanisms remain unclear. This study investigated the anti-aging effects of Bifidobacterium longum subsp. infantis Y46 (BI_Y46) using the model organism Caenorhabditis elegans. We assessed the effect of BI_Y46 on lifespan, developmental cycle, reproductive capacity, body length, locomotion, stress resistance, lipofuscin accumulation, ROS level and gene expression of C. elegans. Findings indicated that BI_Y46 significantly extended C. elegans lifespan by 12.40% (P<0.05). Moreover, BI_Y46 significantly improved C. elegans motility while reducing lipofuscin accumulation and reactive oxygen species levels, without affecting growth, development, or reproductive capacity. Additionally, BI_Y46 enhances the nematode's resistance to oxidative and heat stress. RNA-seq analysis revealed that BI_Y46 bolstered C. elegans' antioxidant capacity by regulating cuticle integrity and drug metabolism. RT-qPCR confirmed that BI_Y46 promoted expression of the antioxidant gene gst-2. This study demonstrates that BI_Y46 extends the lifespan of nematodes by improving stress resistance, providing a theoretical basis for understanding the health benefits of probiotics and establishing a foundation for probiotic-targeted anti-aging strategies.