Objective To investgate the signal transduction and regulation in erythropoiesis by total saponins of Panax ginseng(TSPG) to clarify the mechanism for Panax Ginseng promoting hematopoiesis. Methods The colonyforming ability of mononucear cells(MNCs) from human umbilical cord blood was assayed in methylcellulose assay systems, various dilutions of TSPG(0,10-100mg/L) were then added to each methylcellulose culture mixture; MNC proliferation in response to erythropoietin(Epo) was measured by MTT; To investigate whether the preferential differentiation of MNCs into erythroid lineage cells was caused by an increase in the expression of erythropoietin receptor(EpoR) on the cells, immunoblotting analyses were performed; Immunoprecipitation of JAKSUB>2/SUB>/STATSUB>5 /SUB>was used for the effect of TSPG on Epo/EpoRinduced tyrosine phosphorylation of JAKSUB>2/SUB>/STATSUB>5/SUB>. Results 1TSPG(10-75mg/L) can promote the colony formation of BFU-E, CFU-E, and the preferential differentiation into erythroid lineage cells was induced from 25mg/L of TSPG; 2Using the colorimetric MTT assay, MNCs exhibited proliferous responses to Epo (2×103～5×104IU/L) reaching maximum at 5×103 IU/L Epo;3The addition of TSPG did not increase the expression of EpoR; 4After MNCs were incubated in the presence of with or without TSPG for 24 h, the cells were stimulated with Epo for 0, 2, 5, 30min, and tyrosine phosphorylation JAKSUB>2/SUB>/STATSUB>5 /SUB>was measured. The pretreatment with TSPG enhanced Epoinduced tyrosine phosphorylation of JAKSUB>2/SUB> and STATSUB>5/SUB>(STATSUB>5a/SUB>and STATSUB>5b/SUB>). Conclusion In the present study, we have shown that the Epo/EpoRmediated signals are e