Somatic cell nuclear transfer (SCNT) is the only reproductive engineering technique that can confer genomic totipotency on somatic cell. SCNT is of great significance for animal germplasm conservation, animal husbandry development, and biomedical research. Although many research advances have been made in this technology, the developmental rate of SCNT mammalian embryos is very low, which seriously limits the application of SCNT in animal husbandry and biomedicine. The primary reason for the low efficiency of cloned embryos is somatic cell reprogramming errors or incomplete reprogramming. These errors or incompleteness present as the abnormal expression of imprinted gene Xist, abnormal DNA methylation, and abnormal histone modification. In this review, we summarize the main factors that influence the low development efficiency of mammalian cloned embryos to provide theoretical reference for the research and practice of improving somatic cell cloning efficiency.