Abstract: Six kinds of bio-diesels were prepared with different oil materials, and some important characteristics such as the fatty acid composition, solidifying point and pour point were determined. The rheological properties and influencing factor of bio-diesels were studied systematically with AR-500 rheometers. The results show that the solidifying point and pour point of bio-diesel are affected by the fatty acid composition. The rheological data indicate that the biodiesels display a nonnewtonian flow shear-thinning behavior at low shear rate, and the rheological behaviors are influenced by temperature and shear rate. There is little difference in viscosity for bio-diesels when the temperature is higher than the phase change temperature of biodiesel. It is suggested that the fatty acid composition of biodiesel has no notable influence on viscosity. When the temperature is close to the phase change temperature, the viscosity of bio-diesel will increase greatly and the temperature is higher than the pour point of biodiesel.