The objectives of the present research were to investigate whether embryo culture media have preferences for oxygen tension, to explore the feasibility of using physical lung air to support the in vitro development of mouse embryos, and to evaluate the effect of well of the well (WOW) culture on in vitro preimplantational development of mouse embryos. The results are as follows. First, cleavage rate and blastocyst rate were not significantly different between medium CZB and mKSOM regardless of using 3 gas phases: 4% CO2 + 16% O2 + 78% N2 + 2% H2O (lung air), 5% CO2 + 5% O2 + 90% N2 (5% O2, low oxygen), and 5% CO2 + 95% air (20% O2, high oxygen; P > 0.05), but mean total cell numbers per blastocyst cultured in CZB medium were higher than those in mKSOM when the lung air was used (P < 0.05). Second, when mKSOM was used as the basic medium, the blastocyst rate (22.6%) in the 5% O2 gas phase was notably higher than that in other 2 gas phases (P < 0.05). Third, for the CZB medium, the blastocyst rate was not different significantly among 3 gas environments (P > 0.05). Fourth, both the blastocyst rate (74.6 ± 5.1%) and the mean total cell numbers per blastocyst (76 ± 2) cultured in the WOW system were obviously higher than those in the group culture system (38.2 ± 6.6% and 58 ± 4). Taken together, our results indicate that mKSOM and CZB have preferences for oxygen tension during in vitro culture of mouse embryos, the lung air was reaffirmed to be able to effectively support in vitro preimplantation development of mouse embryos, and the WOW culture system can apparently enhance in vitro developmental competence and blastocyst quality of mouse embryos. L. YS, C. ZB: equal contribution; supported by NSFC (30700574), 863 (2008AA101003).