Maize (Zea mays L.) pot-culture experiments were conducted in this study for exploring the biological responses of maize seedlings to single and joint stress of Cadmium (Cd) and phenanthrene. The results showed that single-Cd treatment with Cd concentration ranging from 0 to 50 mg/kg had no significant influences on the above-ground biomass, root biomass, and the soluble protein of maize seedlings; with the increase of Cd concentrations, the maize leaf SOD activities appeared as an increasing-decreasing trend, while the POD, CAT, APX activities increased persistently. The APX is very sensitive to Cd stress, which increased 38% than control treatment at lower Cd treatment (1 mg/kg). The accumulation of O2-* is one of the main cause of single-Cd toxicity. Under the Cd-phenanthren combined stress, the SOD activity increased at lower Cd concentration (1 mg/kg) , which can reached to 1.66 times of control treatment, and decreased when Cd concentration becomes high. The SOD activity is a sensitive index in response to the Cd-phenanthren combined pollution. Unlike SOD activity, the activities of POD, CAT and APX were obviously induced by combined pollution of Cd and phenanthren; but these enzyme activities decreased when compared with the single-Cd stress, which suggested that the combined toxicity of Cd and phenanthrene is stronger than the single-Cd stress. And the accumulation of O2-* and *OH is one of the main cause of Cd-phenanthrene combined toxicity.