Abstract: Biodiesel is a kind of clean and renewable fuels.More and more countries are studying and using biodiesel as alternative fuels. Biodiesel is easy to crystallize under low-temperature because of high solidification point (SP) and high cold filter plugging point (CFPP). Crystallization could plug the pipeline and the filter net of the engine to make it out of work. It becomes an important task of the biodiesel research to how to reduce the SP and the CFPP of the biodiesel. The researches on improving the low-temperature fluidity of the biodiesel at home and abroad, the studying on pour point depressant, and the mechanism of pour point depression are reviewed in this paper.