Objective To study the impact of blood clots in the oocyte-corona-cumulus complexes (OCCC) during in vitro fertilization and embryo transfer (IVF-ET).Methods The OCCCs were harvested from the patients undergoing long protocol ovarian hyperstimulation.The OCCCs with blood clots removed or not,were randomly grouped into A or B.The OCCCs without blood clots were group C (the control).Results The patient’s age,infertility duration,the average GN consumption,the average days of superovulation and an average number of harvested oocytes showed no significant difference in the 3 groups.The fertilization rate and 2PN rate in group A were the highest,which were 85.4％ and 71.1％,respectively,followed by group C,which were 77.5％ and 64.9％,respectively.The lowest fertilization rate and 2PN rate were in group B,75.8％ and 62.2％,respectively.Those in group A were significantly higher than those in groups B and C (P＜0.01 ),while there was no significant difference between group B and group C.The implantation rates and pregnancy rates showed no significant difference in the 3 groups after transplantation,even if group A got the highest rate among the 3 groups.Conclusion Removing the blood clots in OCCC can improve the outcome of IVF-ET without increasing the cost and complexity of the operation.