In the study, the effects of dimethyl phthalate (DMP) on the antioxidant defense capacity and immune functions of human erythrocytes were experimentally explored. DMP affected the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) and the contents of glutathione (GSH) and malondialdehyde (MDA) in erythrocytes, thus impairing the function of antioxidant defense system of erythrocytes. When DMP concentration increased from 0 to 28 μmol L, the SOD and GPX activities were increased firstly and then gradually decreased. When DMP concentration was below 20 μmol L, the relative activity of SOD was enhanced by DMP and the effect was known as hormesis. The relative activity of GPX was also increased when the concentration of DMP was below 12 μmol L. The CAT activity was more significantly inhibited by DMP than the activities of SOD and GPX, whereas the relative GSH content was increased by DMP. MDA levels were significantly changed after the exposure to DMP (0-24 μmol L). The experimental results of the activity of SOD and CAT, and the content of MDA also suggested that DMP could inhibit the immune functions of red blood cells (RBCs), which were further proved by the decrease of two indicators (RBC-Cb and RBC-IC) due to the destruction of Cb receptor with immune adherence function on erythrocyte membrane. The study provides a deep understanding of the toxicity of DMP on erythrocytes.