Abstract: To prepare paclitaxel-schisandrin B microemulsions containing paclitaxel (Paclitaxel-Schisandrin B microemulsions, PSM) and assess the stability, acute toxicity and anti-tumor activity of PSM.PSM was prepared using polyethylene glycol-two stearoyl acyl phosphatidylethanolamine (PEG-DSPE) , oleic acid, schisandrin B and paclitaxel.The particle size distribution and Zeta potential of PSM were determined using laser particle /Zeta potential analyzer while the loading function of PSM was with the use of Sephadex G50 column.PSM was kept in the cold (7℃) and dark place for 1 year, and then the changes of PSM in its particle size and paclitaxel content were measured to study of its stability.The acute toxicity of PSM was evaluated by comparisons of the acute toxicity of paclitaxel and PSM.The anti-tumor activity of PSM was studied using S180 animal sarcoma model.The diameter, Zeta potential and drug loading efficiency of PSM were (98.2± 12.6) nm, (-29.6±5.8) mv, 98.2%±0.5% (n=3) , respectively.Kept for one year, there was no significant change in the particle size of PSM while the paclitaxel content of PSM was decreased to 91.8% of its original amount, no more than 10%.After intravenous injection, the anti-tumor activity of PSM was enhanced visibly compared with the free paclitaxel however the acute toxicity of PSM was much lower than the free paclitaxel.PSM might become a better anticancer medicine than paclitaxel injection.