Abstract： Objective To investigate the proliferative differences of adipose-derived stem cells (ADSCs) from neonatal suckling SD rats (5-d-old) and adult ones under the same culture condition.Methods ADSCs were isolated from the subcutaneous adipose tissues of neonatal suckling SD rats and adult ones,and then,type Ⅰ collagenase digestion was employed to obtain the ADSCs; the morphology of these cells was detected.The expressions of such cell surface markers as CD45,CD29 and CD90 were observed. The number of ADSCs on the 4th d of culture under the same condition and with the same planted density was compared between the neonate and adult rats. In vitro culture of the second generation of ADSCs was performed in the 96-well plates, and CCK-8 and alamar blue kit were employed to compare and quantitate the proliferative differences; optical density was observed by microplate reader. Results The ADSCs from neonatal SD rats and adult ones expressed the stem cell biomarkers: the expression of CD45 was negative, and that of CD29 was 98.04％ and 93.17％,respectively,and that of CD90 was 94.92％ and 93.3％,respectively,for neonate SD rat and adult ones.The cell counting results indicated that the number of ADSCs from neonatal rats ([8.87±0.13]×105 cells) was larger than that of adult ones ([4.51±0.36]×105 cells) after being cultured under the same condition and at the same planted density. The optical density value of ADSCs in neonatal rats was significantly higher than that in adult ones on the 6th and 7th d of culturing detected by CCK-8 kit and on the 2nd-7th d of culturing by alamar blue assay. Conclusion The proliferative ability of ADSCs from neonatal rats is greater than that of adult ones.