This paper compared the variation trend of the output and consumption of diesel and the difference of the qualities of different sources diesel with the standard of Ⅵ diesel in China, and analyzed the composition, quality and problems of diesel pool in detail. It is considered that the most important problems in diesel quality upgrading process is how to reach the standard of diesel density and cetane number (including cetane index), rather than diesel sulfur content. Therefore, some countermeasures were put forward, such as identify the difference between cetane number and cetane index, optimizing crude oil processing, hydro?converting inferior diesel and adjusting the product structure of refinery.