Arsenic and copper, two ubiquitous pollutants, can be oxidative stress inducers when organisms are heavy or chronically exposed, causing adverse effects on digestion and absorption function, resulting in potential losses to poultry husbandry. The present study examined the effects of arsenic trioxide (30mg/kg)- and copper sulfate (300mg/kg)-mixed foods, administered alone or in combination for 12weeks, on various biochemical indices of oxidative stress and immunity in the small intestines of Hy-line chickens. The results showed that for the first four weeks of exposure, both the redox and immune systems were unaffected. Subsequently, exposure to arsenic or copper significantly increased the level of lipid peroxidation (malondialdehyde and ability of anti-hydroxy radical) concomitant with a collapse of the antioxidant system (catalase and glutathione peroxidase), in a time-dependent manner. An increase in the mRNA and protein levels of pro-inflammatory indicators (nuclear factor kappa B, cyclooxygenases-2, tumor necrosis factor-α and prostaglandin E2 synthases) with a definite tendency toward Th1 (Th, helper T cell) cytokines was observed in both arsenic and copper treated chickens. Histologically, the destruction of the biofilm structure and inflammatory infiltrates was observed. Thus, in the intestine, heat shock proteins play protective roles against tissue damage. In some cases, we observed that the tissues of the small intestine were more sensitive to arsenic than to copper. Moreover, co-exposure induced more serious intestinal toxicity than single treatment group, and this mechanism needs further exploration.