Abstract: 【OBJECTIVE】The objective of this study is to empolder further porcine genetic potential and provide large number of oocytes in high quality for embryo biotechnology such as in vitro fertilization, cloning and transgenic technology.【METHOD】To study the optimal maturation methods, one-step and two-step methods were adopted to maturate porcine preantral follicle oocytes regarding eduction of first polar body as maturation symbol. 【RESULTS】The results showed that none of the oocytes recovered from any of these experiments reached metaphase Ⅱ stage after IVM. However, when the cumulus oocyte complexs (COCs) from follicles cultured for 5 days were cultured for another 12d in vitro, oocytes grew to a mean diameter of 102.68μm(102.68±12.21), which is close to that of full-sized porcine matured oocytes.【CONCLUSION】Oocytes can grow close to the full-sized matured oocytes with two-step to maturate porcine preantral follicle oocytes. The results indicated that method of two-step to maturate porcine preantral follicle oocytes was viable.