Abstract: Based on the viscosity-temperature curves of soybean oil, waste oil and peanut oil biodiesel, the cloud points of biodiesels were obtained. The amount and composition of precipitated crystals of biodiesels at different temperatures were measured by high speed centrifugation and gas chromatography (GC). It is found that the solid filtrated from the biodiesel is not a pure crystal, but a mixed one mainly composed of saturated fatty acid methyl esters(FAMEs). The amount of FAMEs with high carbon number is more than that with low carbon number. The higher content of saturated fatty acid methyl ester, the higher cloud point and viscosity and the more crystal precipitation as well. The diesel will exhibit worse cold flow properties.