To serve as a diesel fraction, light cycle oil (LCO) is commonly hydrotreated by a complicated and widely used industrial process under high temperature and high pressure. In this study, the system dynamics (SD) methodology is, for the first time, introduced to dynamically simulate this commercial hydratreating process along the axial positions of the hydrotreator. The proposed SD model is fully presented and validated by both direct and indirect structure validation tests. The efficiencies of the hydrodesulphurization (HDS), hydrodenitrogenation (HDN), and hydrodearomatization (HDA), and the consumption rate of H-2 gas during the hydrotreating process are also simulated. The influence of the operating conditions such as the liquid hourly space velocity (LHSV) and the inlet feed temperature on these efficiencies and H-2 consumption is investigated numerically. (c) 2008 Elsevier B.V. All rights reserved.