Bai-Hasan wide distillate derived from Bai-Hasan crude oil (having a boiling range from initial boiling point to 823K), was hydrotreated in a Trickle Bed Reactor using the commercial cobaltmolybdenum on alumina (Co-Mo/_γ-Al₂O₃) as a catalyst. The reactor temperature was varied from 603 to 673 K and the liquid hourly space velocity (LHSV) from 0.6 to 1.9 hr^-1, keeping constant hydrogen to oil ratio (H₂/Oil) and hydrogen pressure at 350 L/L and 3MPa, respectively. In order to obtain useful models for hydrodesulfurization (HDS) process, the accurate estimation of kinetic model of the relevant reaction scheme were required. Thus, kinetic model of sulfur removal was studied by using an optimization technique based on pilot plant experiment. The minimization of the sum of the squared errors (SSE) between the experimental and estimated concentrations of sulfur compound in the products was used as an objective function to determine the kinetic parameters via non-linear regressions. The predicted product concentration showed very well agreement with the experimental data for a wide range of operating conditions with absolute average errors less than 5%.