Abstract: The purpose of the study was to improve the total industrial application efficiency of dairy cow somatic cell nuclear transfer （SCNT）by optimazing the in vitro producting conditions of dairy cow SCNT embryos. In this study, the effect of different factors, such as enucleation method, sources of donor cell different ages cows, serum starvation, and gas component condition, on the efficiency of SCNT were studied. The results demonstrated that there were no significant differences on the rate of enucleation and the rate of blastocyst（100% and 24.83% in the fluorescent-assistant group and 92.44% and 28.26% in the blind-suction group, respectively）（P>0.05）. However, the method of blind-suction was easier to operate and more efficiency. The age of donor cows showed no significant impact on the rate of blastocyst（31.43% and 25.68%, respectively）. There was no significant difference on the rate of blastocyst between serum-starvation and non-starvation group（24% and 29.9%, respectively）, and there was no significant difference on the rate of blastocyst between high-oxygen and low-oxygen group（28.26% and 31.55%, repsctively）. Conclusionly, the results showed that the optimized condition for industrial production of dairy cow SCNT embryos was as follows ：donor cells without serum-starvation could be injected into ooplasm enucleated by blind-suction to construct cloned embryos. Then, fused cloned embrys should be cultured under sealed condition with 5% CO2, 5% O2, and 90% N2 to get a reasonable rate of blastocyst.

Key words: Dairy cows, Somatic cell, Ennuclear, Nuclear transfer, Reconstructed embryos