Somatic cell nuclear transfer (SCNT) is a technology in which a somatic nucleus is transferred into the cytoplasm of a matured oocyte - reconstructed embryos have the capacity to develop to term. Why somatic cells can be reprogrammed by oocytes - the answer for this question must exist in the cytoplasm of matured oocytes. In this review, totipotent characters of matured oocytes were discussed, which may confer matured oocytes with the capacity to reprogram somatic nucleus. Moreover, the procedure of SCNT also makes a possibility for somatic nucleus to be reprogrammed by oocytes. Compared with fertilized embryos, embryos derived from SCNT exhibit low developmental ability; the barricades in reprogramming process and their possible reasons were also discussed. This review maybe can benefit the mechanism research of SCNT technology and can make contribution for improving the efficiency of this technology.