Abstract: Objective: To evaluate the antioxidant capacity and anti-aging potential of Laminaria japonica oligosaccharides 2 (LOs2) in Drosophila melanogaster. Method: Wild-type vestigial-wing D. melanogaster were reared on standard medium supplemented with LOs2 at low (0.25%, w/w), medium (0.50%), or high (1.00%) doses. The antioxidant and anti-aging effects of LOs2 were evaluated by determining the activity of superoxide dismutase (SOD), the content of malonic dialdehyde (MDA), the activity of catalase (CAT) in D. melanogaster, and the lifespan experiment of D. melanogaster. Result: Relative to the blank control, the 1.00% LOs2 group showed the highest T-AOC, increasing by 45.87% in females and 76.21% in males. MDA levels were markedly reduced (82.77% in females, 61.24% in males) (P<0.05). SOD and CAT activities rose significantly at 1.00% LOs2 in both sexes (P<0.05). The 1.00% LOs2 group showed a 54.13% increase in female lifespan and a 72.00% increase in male lifespan compared to the blank control group. Consistently, qPCR revealed marked up-regulation of SOD1, SOD2, and CAT in the 1.00% group (P<0.05). Conclusion: These findings suggested that LOs2 attenuated the accumulation of excessive ROS and MDA by up-regulating the expression of SOD1, SOD2, and CAT genes, thereby delaying aging of D. melanogaster. LOs2 exhibited favorable antioxidant activity in vitro and in vivo, as well as potential anti-aging effects.