Objective To explore the developmental characteristics and gene expression patterns of mouse embryonic stem cells (mESG)derived embryoid bodies(EBs). Methods The EBs were derived from undifferentiated mESCs by suspending culturs in leukemia inhibitory factor (LIF) free media. The morphological character istics and genes expression related to the sequential stages of embryonic development was detected by morphological observation, immunohistochemistry and RT-PCR over 90 day’s duration. Results The primary round and packed EBs were formed within the first 24 hours of suspension culture, which also comprised many of undifferentiated mES. The simple embryonic bodies formed through 3day of differentiation, and the EBs developed to embryonic cavity-like structures at 9 days. Subsequently, the EBs formed a typical and integral trilaminar structure at 11 days. Early stage EBs always developed to a columnar epithelium with the formation of a central cavity and was also cystic. From the seventh week on, the EBs growth ceased. At fifteen day, the EBs derived from mES expressed a trilaminar protein markers Nestin and cTnT, The expression of other genes associated embryonic development such as Vimentin, Nestin , Flk-1、Gata-1, Transthyretin and α-fetoprotein were detected by RT-PCR . Conclusion EBs can differentiate into the dimensional cell aggregates and initiate mES differentiation procedures during the long periods of culture in vitro. Our results provided a molecular