The distribution of active sites on a nitrided CoMo/Al2O3 catalyst was studied based on a non-parametric determination method using the conversion rate of hydrodesulfurization of dibenzothiophene. This method makes use of a Fredholm integral equation of the first kind and provides the activity distribution of the catalytic active sites. These active sites were discussed based on the reaction products during the reaction, the surface properties by CO adsorption and X-ray photoelectron spectroscopy. The distribution function revealed two active sites of the nitrided catalyst with different rate constants for the hydrogenation of dibenzothiophene on Site I and for the C _ S hydrogenolysis on Site II. Site II had a 58.3 times higher rate and 1.27 times the population than Site I for the 973 K-nitrided catalyst.