Abstract: To observe antitumor activity and inducing apoptosis of low molecular weight polysaccharide isolated from Agaricus blazei Murill (LMPAB) on sarcoma 180 in mice. Methods The BALB/c mice inoculated in armpit with S180 cell suspension were treated by intraperitoneal injection of LMPAB 50 100 and 200 mg/（kg&#8226;d） for 7days, The mice were sacrificed after 24h and tumor tissues were weighed respectively. Tumor cell apoptosis was detected by Annexin-Ⅴ-FITC/PI (Flow cytometry). Results In LMPAB group 200 mg/（kg&#8226;d） (0.695±0.096) and Polyporus polysaccharide group (0.704±0.262) tumor weight reduced compared with the model group（1.038±0.262, P<0.01), Inhibitory rate of sarcoma 180 in mice treated with 50, 100, 200 mg/（kg&#8226;d） LMPAB was 9.5%, 23% and 32%, respectively. The apoptosis rate of sarcoma 180 cells in mice treated with 50, 100, 200 mg/（kg&#8226;d） LMPAB was (39.21±3.85) %, (32.17±5.10)% and (18.71±2.52)%, respectively, higher than that in the model group mice (10.98±1.55)%. Conclusion LMPAB significantly inhibited the growth of sarcoma 180 subcutaneously implanted in mice, possibly through inducing apoptosis of tumor cells.