Abstract: The improvement of cetane number (CN) was studied over Ni-Mo-W catalyst in the light cycle oil (LCO) hydro-upgrading processing in pilot plant. The effect of the processing parameters on improving cetane number of LCO was investigated. The results indicate that 7-13 cetane number increment is observed under 6.4 MPa and other suitable operation conditions. The main factor influencing the increment of cetane number of LCO is the aromatics saturation reactions. Other operation parameters, such as temperature, LHSV and H2 to oil ratio have also a significant influence. The suitable reaction conditions are helpful to increase CN of diesel fraction through aromatics saturation.