Objective To study the effect of Peroxiredoxin Ⅱ on development of mouse preimplantation embryos in vitro and to investigate the possible action of Peroxiredoxin Ⅱ on preimplantation embryonic development. Methods One-cell embryos collected from the oviduct of the superovulated mice were cultured in microdrops of medium for 48?h.The effect of peroxiredoxin Ⅱ antibody on the development of embryo in vitro was observed,and the percentage of embryos developing to 2-and 4-cell stage of embryos was used as evaluation criteria.With redox-sensitive fluorescence probe 2′,7′-dichlorodihydroflurescin diacete(DCFH-DA),reactive oxygen species(ROS) induced by Peroxiredoxin Ⅱ antibody was monitored in mouse embryos after 24?h culture by laser confocal scanning microscopy. Results The embryonic development rate from 2-cell stage to 4-cell stage was decreased significantly by Peroxiredoxin Ⅱ antibody in the dilution of 1∶100 and 1∶200,but Peroxiredoxin Ⅱ antibody had no inhibitive effect on development from 1-cell to 2-cell stage.Moreover,Peroxiredoxin Ⅱ antibody in the dilution of 1∶200 induced increase in the production of reactive oxygen species in mouse embryos from 24?h culture of one-cell embryo.Conclusion Peroxiredoxin Ⅱ antibody induced the generation of “2-cell block” by increasing the production of reactive oxygen species(ROS) in mouse embryos.These results also indicated that Peroxiredoxin Ⅱ may reduce or eliminate ROS in preimplantation embryos and promote the development of preimplantation embryos.;