Abstract: A reformation theory of pour point depressant is verified and the reformation law of pour point depressant is obtained by means of research on reformation of pour point depressant. The laboratory experiment and application in some oil pipelines with GY-3 serial pour point depressants show that this kind of depressant can significantelly improve the low-temperature flowability of waxy crude oils transported by Weijing Oil Pipeline, ZhongLuo Oil Pipeline, PuLin Oil Pipeline and HuaGe Oil Pipeline, as well as Tarim Oil, Daqing Oil and Renqiu Oil, with remarkable stability.