This study was aimed to investigate the effect of GATA-2 over-expression on function of mouse fetal liver hematopoietic stem cells. GATA-2 was introduced into mouse fetal liver cells via retrovirus mediated transduction with GFP as a detecting marker. Flow cytometry, colony-forming assay and cell cycle assay were used to detect the biologic changes of these retrovirus infected mouse fetal liver hematopoietic stem cells. The results showed that GATA-2 over-expression increased the Lin(-)Sca1(+)C-Kit(+) (LSK) population dramatically. Cell cycle of LSK cells didn't show abnormal, while colony forming ability decreased significantly. These data indicated that GATA-2 over-expression inhibited definitive differentiation of mouse fetal liver hematopoietic stem cells. It is concluded that over-expression of GATA-2 can significantly raise the LSK cell proportion in mouse fetal liver and inhibit the differentiation capability, the underlying mechanisms may be related to up-regulation of Hes-1, which may lead to the blocking of cell differentiation at the stem/progenitor cell stage.