Abstract: Experiments were conducted to study the effect of different vitrifications, straw and open pulled straw(OPS ), on survival, in vitro maturation, in vitro fertilization, and post-fertilization development of vitrified-thawed immature bovine COCs(cumulus oocyte complex).The results as follows: The recovery of post-thaw morphologically normal COCs in straw and OPS were 59.4%±4.3% and 77.9%±4.1% respectively(P<0.01)；The maturation rates were 48.2%±5.3% and 66.0%±5.8% respectively（P<0.01）；The cleavage rates were18.5%±2.0% and 32.8%±1.4% respectively（P<0.01）；The percentage of 8-cell embryo were 148%±2.5% and 24.8%±1.5% respectively（P<0.01）；The percentages of morula in straw , OPS and fresh oocytes were 0, 5.3%±1.1%and 21.0%±3.8% respectively（P<0.01）；The percentage of blastocyst in straw , OPS and fresh oocytes were 0, 4.0%±1.0%and 17.1%±2.7% respectively （P<0.01）.In conclusion,the vitrified-thawed immature bovine COCs by OPS could develope to morula and blastocyst stages after IVF,although it was low.