Objective To investigate the effect of osteopontin(OPN) on in vitro fertilization and embryo development of the mouse. Methods Totally 120 females and 30 males of Kunming white strains mice were used in our experiment.Mouse sperms,ova,pronucleus embryos,and 2-cell embryos were treated with various concentrations of OPN antibody (OPN-Ab).Fertilization,cleavage and embryo development were observed.Results When mouse sperms and ova were pretreated by various concentrations of OPN-Ab,the fertilization rate was significantly lower than that of the control group(EM>P/EM> 0.01).When pronucleus embryos were pretreated by various concentrations of OPN-Ab,there were no significant differences in the cleavage rate between the 0.01mg/L OPN-Ab and the control group (EM>P/EM> =0.052).The cleavage rate in the 1.00mg/L OPN-Ab group was significantly lower than those in 0.01mg/L (EM>P/EM> 0.01) and 0.10mg/L OPN-Ab group (EM>P/EM> 0.05).Embryonic development was inhibited when 2-cell embryos were pretreated by various concentrations of OPN-Ab.There were no significant differences in both the 4-cell and the 8-cell cleavage rates between in the 1.00mg/L OPN-Ab group and in the 0.10 mg/L OPN-Ab group (EM>P/EM> ＞0.05),but their blastocyst formation rates were lower in the 1.00mg/L OPN-Ab than those in the 0.10mg/L OPN-Ab group (EM>P/EM> 0.01).The blastocyst formation rates of both 4-cell and 8-cell groups were significantly lower in the 1.00mg/L OPN-Ab group than those in the 0.01mg/L OPN-Ab group (EM>P/EM> 0.01). Concl