In order to study the effects of physical and chemical properties of coal-to-diesel on diesel engine emission, WHTC, WHSC and WNTE tests were conducted on a diesel engine equipped with DOC+DPF+SCR+ASC posttreatment devices in line with the China Ⅵ emission regulation. Different fuels were used including D1 (blended fuel of coal direct liquefied fuel and coal indirect liquefied fuel in proportion), D2 (blended fuel of coal direct liquefied fuel and cetane number agent in mass ratio), G6-D1 (blended fuel of D1 and G6 fuel with 1∶1 mass ratio), G6-D2 (blended fuel of D2 and G6 fuel with 1∶1 mass ratio) and China Ⅵ diesel fuel. The results show that the emission results of all the five fuel samples meet the requirements of China Ⅵ emission regulation. D1 fuel has the best comprehensive emission performance, indicating that the high performance clean coal-to-diesel can be obtained by blending DDCL and DICL coaltodiesel in proportion with the addition of appropriate additives. The emissions of G6-D1 and G6-D2 fuels meet China Ⅵ standard and are 20% lower than those of G6 fuel in PM, CO and THC emissions, and hence the blended fuel prepared by China Ⅵ G6 diesel and coal-to-diesel has the advantages of G6 fuel such as high cetane number and low cost and the advantages of coal-to-diesel such as low sulfur content and low polycyclic aromatic hydrocarbons content. Accordingly, the high efficiency, clean and low cost coal-to-diesel can be prepared.