Abstract: Objective To investigate changes of serum total oxidation status (TOS) and total antioxidant status (TAS) and their association with apolipoprotein (a) [Apo(a)] in patients with polycystic ovary syndrome (PCOS) combined with infertility. Methods Ninety patients with PCOS and infertility were selected as the study group, including 45 patients treated with antioxidants combined with Diane-35(group A) and 45 with Diane-35 therapy only (group B), with 45 healthy volunteers with normal menstruation and normal dual phase basic body temperatures as the control group. Serum TOS of the participants was determined by dual xylenol orange method, and serum TAS was determined with ABTS method; plasma Apo(a) level was determined by dual wavelength immune transmission turbidity method. Results Before treatment, serum TOS, OSI, and Apo (a) levels were significantly higher and TAS level was significantly lower in the study group than in the control group (P<0.05). Serum TOS, OSI, and Apo (a) were significantly lowered and TAS was significantly increased in group A after the therapy as compared with the levels before therapy and the levels in group B. The rate of natural recovery of menstruation was significantly higher and the incidence of cardiovascular disease was significantly lower in group A than in group B (P<0.05). Pearson correlation analysis showed that serum TOS and OSI were positively correlated with plasma Apo(a) (r=0.524 and 0.531, P<0.05), and serum TAS was negatively correlated with plasma Apo(a) (r=-0.519, P<0.05). Conclusion Antioxidant therapy can lower TOS, OSI and Apo(a) levels and increase TAS level to lessen oxidative stress, improve the prognosis, and reduce the risks of cardiovascular disease in patients with PCOS and infertility.