Diabetes mellitus (DM) is a metabolic disease of origin endocrine disease, whose main biochemical characteristic is chronic hyperglycemia. Triggers serious biochemical processes for the body such as oxidative stress (OE). The objective of this study was to evaluate the protective effect of vitamin C (VitC) on EO in rats Sprague-Dawley with Streptozotocin (STZ) -induced DM. 16 rats were used (100 ± 20 g), divided into 4 groups: 1) control, 2) STZ (diabetic), 3) VitC + STZ, 4) VitC. In homogenized from liver I know determined the concentration from malondiahaldehyde, dienes conjugated and protein totals. By other part I know they determined the activities from superoxide dismutase Y catalase. Too I know measured the hurt to the DNA hepatic by test Kite. The results I know they analyzed statistically through Program SPSS version 17.0 for Windows. Applied a Anova Y a test from comparison multiple DMS (p <0.05). It could show that in the group from animals treaties with VitC decreased the levels from glucose and the generation from EO; too there was less hurt of the DNA by radicals free. These data allow infer that the VitC exercises a effective action antioxidant and protective of the liver before the permanent production from radicals free; further from to be effective in the repair and conservation of the DNA.