The achievements of cetane number improvers of diesel fuel was introduced. The working mechanism of improvers in improving the cetane number of diesel fuel was stated,the traditional and the new type of cetane number improvers were contrasted,the future trends of cetane number improvers were pointed out. The classification and the development of cetane number improver for diesel fuel were nitric acid esters,the effects of such substances were good,but extremely increased the risk because of the instability of the synthesis,storage and transport. A good effect could be achieved if the other substances were added into nitric acid esters at a proper proportion. Environmental- friendly cetane number improvers have broader application prospects.