Abstract： Objective To investigate the mobilization effect of low-does granulocyte-colony stimulation factors(G-CSF) on allogenic peripheral stem cell transplantation (PBSCT) and the best acquisition time for haemopoietic stem cell. Methods G-CSF was administered subcutaneously at 5μg·kg~(-1)·d~(-1)to 108healthy donors. The mobilization effects were assayed by mononuclear cell count,flow cytometry and colonyforming units analysis.Results Onfourth day,fifty day and sixth day, the ratio of CD_(34)~+ were (0.71 ±0.08)%, (1.09±0.09) %, (0.57±0.08) %, respectively. The CFU-GM yield were (93.33±44.51)/10~5MNC, (124.61±57.85)/ 10~5MNC, (80.25±49.24)/10~5MNC, respectively. The number of CD_(34)~+ were (3.33±1.36)×10~6/kg, (4.14±1.67) ×10~6/kg, (2.79±1.47)×l0~6/kg, respectively. The ratio and number of CD_(34)~+ cell of PBSC collections of fifth day was higher than that of the fourth day (P <0.05). And the fourth day was higher than that of the sixth day(P < 0.05). Twice day (fourth day and fifth day) collection can obtain enough CD_(34)~+ cell for PBSCT. There were no significant adverse effects. Conclusion Low-does G-CSF takes good effects on the mobilization of PBSC. And it was better to collect stem cell on fourth day and fifth day rather than on fifth day and sixth day after mobilization.