Background: The synchronization of the uterus and mature eggs at the molecular level is the key factor in embryo transfer, and the regulation of synchronization depends on a variety of cytokines. C-reactive protein (CRP), as the first acute phase reaction protein, is involved in the entire process of embryo transfer. The study is designed to investigate the correlation among CRP, sex hormone, controlled ovarian hyperstimulation (COH) cycle, and pregnancy outcome. Materials and Methods: Ninety-two patients who accepted in vitro fertilization (IVF) treatment cycles because of tubal factor were included in the study. Seventy treated cases were included to complete final analysis with the full set of results. Respectively on the second day of the menstruation (Day-2) in gonadotropin-releasing hormone agonist (GnRH-a) short program treatment, on the morning in human chorionic gonadotropin (hCG) treatment (Day-hCG) and the embryo transplant day (Day-ET), plasma CRP level was tested by enzyme-linked immunosorbent assay (ELISA). The correlativity among CRP level, sex hormone, COH, and pregnancy outcome was analyzed by statistical methods. Results: In the short program GnRH-a of 70 cases, there was no relationship between serum CRP level and the infertility age, gonadotropin (Gn) dosage, number of oocytes retrieved, the number of normal fertilization, and sex hormone. In the short program of GnRH-a, the change of serum CRP levels in Day-2, Day-hCG, Day-ET: serum CRP in Day-2 < Day-hCG < Day-ET and the level of serum CRP gradually increased in Day-2, Day-hCG, and Day-ET in both the pregnant group and non-pregnant group. In non-pregnant group, the ratio of hCG / D2 and ET / hCG-day were significantly higher than the pregnant group. The area under receiver operating characteristic (ROC) curve was 0.806, indicating the accuracy of diagnostic tests is medium. the authors chose the point which presents the ratio of CRP in Day- ET to Day-hCG which was less than 1.752 as a predictor of treatment outcome, the sensitivity of the experiment was 77.8%, and the specificity 75%. Conclusion: CRP as a sensitive inflammatory marker, CRP ratio of Day-ET/ Day-hCG could be a predictor of treatment outcome by ROC curve analysis in COH program.