Abstract: In order to study the effect of temperature on the kinematic viscosity of ternary fuel blends,the biodiesel（soybean oil/Jatropha oil/waste cooking oil）-ethanol-diesel fuel blend are prepared. A mathematical model which could precisely describe the influence of temperature on kinematic viscosity of ternary fuel blends is established. The complex correlation coefficient of the model is higher than 0.99 while the maximum error is 0.03. According to the fitting results, the highest viscosity gradient of waste cooking oil biodiesel-ethanol-diesel fuel blend would be influenced by temperature greatly and the flow property of which is also changed remarkably. Furthermore, the critical preheating temperature values for three kinds of ternary fuel blends are 59.1 ℃, 63.4 ℃ and61.7 ℃,respectively and the operating cost are lowest and the atomization effect are the best when the blends are preheated at the critical preheating temperatures.