OBJECTIVE To observe the effect of Cangfu Congxian Decoction (CCD) on oxidative stress in granulosa cells of polycystic ovary syndrome (PCOS) patients. METHODS Forty PCOS patients underwent in vitro fertilization-embryo transfer (IVF-ET) were assigned to the treatment group and the control group 1 according to random digit table, 20 in each group. Patients in the treatment group took CCD (200 mL, once in the morning and once in the afternoon) 2 months before IVF-ET, while those in the control group 1 took no Chinese medical decoction. Recruited were another 20 patients undergoing IVF-ET for tubal factors (as the control group 2). The clinical effect of IVF-ET were observed, including oocyte retrieval number, 2 pronuclear (2PN) fertilization rate, good quality embryo rate, clinical pregnancy rate, and ovarian hyperstimulation syndrome (OHSS) induced transplantation cancel rate. The expression of relative oxygen species (ROS) in granulosa cells was detected using cell immunofluorescence combined with confocal microscopy and FCM. RESULTS Compared with the control group 1, occyte retrieval number, 2PN fertilization rate, and good quality embryo rate increased in the control group 2 and the treatment group (P <0. 05). OHSS induced transplantation cancel rate decreased in the control group 2 (P < 0.05). Fluorescence intensity of ROS decreased in the treatment group and the control group 2, as compared with the control group 1 (P < 0.01). CONCLUSION CCD increased good quality embryo rate by down-regulating the expression of ROS protein in ovarian granulosa cells, and correcting in vivo oxidative stress.