Abstract: Phytolacca acinosa polysaccharides Ⅱ(PAP-Ⅱ), a kind of polysaccharides isolated from Phytolacca acinosa Roxb with MW 40 kDa, on lymphocyte proliferation and colony stimulating factor (CSF) production from splenocytes in vitro, was studied. The radioactivities of ³H TdR uptake by lymphocyte and bone marrow cells were used to determine the ability of lymphocyte proliferation and CSF production respectively. PAP-Ⅱ was found to significantly augment splenocyte proliferation in a dose—dependent fashion, and significantly enhance Con A (1, 2. 8 μg·ml^-1) and LPS (3, 10, 30 μg.ml^-1) induced lymphocyte proliferation at concentration of 31～125 μg.ml^-1. As the concentration of PAP-Ⅱ increased, significant suppression of Con A—induced lymphocyte proliferation was observed. Induction of CSF by PAP-Ⅱ from splenocyte was confirmed at the present study. The optimal dosage was 100 μg.ml^-1 and the optimal effect occurred on day 5. These results suggest that PAP-Ⅱ can augment immunological function and enhance hematopoiesis.