Objective To investigate the significance of EGF in the in vitro maturation, fertilization, and pre-implantation development of the immature oocytes. Methods The immature oocytes were isolated from the ovaries of the rats. The germinal vesicle (GV) oocytes were cultured in the EGF solutions at concentrations of 0(control), 0.5, 1, 2.5, 5 and 10 ng/ml Ham’s F10 culture media. The status of germinal vesicle break-down(GVBD) and the extrusion of the first polar body (PB1) were observed. The achieved MⅡoocytes were then inseminated in vitro; and the pronuclei (PN) and the pre-implantaon development were observed. The gradeⅠ-Ⅱ4-cell embryos were selected and implanted into the fallopian tube of the rats with the 1 day pseudogestation. Follow-up observations were made till the delivery. Results After GV oocytes were treated with EGF solutions at concentration of 1, 2.5, 5 and 10 ng/ml for 12, 16, 20, and 24 h, the GVBD in the GV cumulus-oocyte complexs(COC) have better outcomes than that of the control group(P