Abstract: For diesel transported by long-distance pipeline, its quality decreases with the increase of transportation distance. Here, the factors affecting the diesel transport quality of the Western Products Pipeline were studied through batch tracking and sampling test. The results show that the average flash point attenuation of 0^# and －35^# diesel at the terminal station are 5.75 ℃ and 3 ℃, respectively. Thus, the recommended minimum flash point of 0^# and －35^# diesel filled into the pipeline should be 66 ℃ and 48 ℃, respectively. In the case of batch transportation, the quality attenuation of diesel is relatively serious due to the great difference of the quality between adjacent oil products, and the quality of diesel attenuates more seriously with the increasing shutdown time of pipeline. Hence, the shutdown of pipeline should be minimized. The impurities in the pipeline can also result in the quality decrease of diesel transported. So, regular pipeline pigging is conductive to improving the quality of pipeline diesel. Additionally, change of pipeline flow, which is greater than the critical flow, has little influence on the quality of diesel transported. Conclusively, the research results could provide theoretical reference for economic and efficient operation of long-distance products pipelines.