Bai-Hassan reduced crude (350°C + ) was hydrotreated in fixed bed reactor with commercial Ni-Mo-alumina catalyst. H and quantitative C NMR are used to derive statistical average structure parameters of feedstock and hydrotreated products. The main aromatic hydrocarbons (of type Car,H + Car,CH3 + Car,n + Car,I) of hydrotreated products decreases by temperature, (at mild conditions) particularly at lower space velocity. The severe operating conditions increases the main aromatic hydrocarbons. An approximate inverse correlation is observed between the behaviour of saturated hydrocarbons and the aromatics of type Car,H + Car,CH3 + Car,n + Car,Iduring hydrotreating process. Higher temperatures show an increase in the percentage of alkyl aromatics of type Car,alkFurthermore, the severe operating conditions promotes the formation of the alkyl aromatics with Hα(ArCH3) while it decreases the alkyl aromatic having H8and H8The kinetic study of napthenes formation indicates that this reactin is well correlated with a first-order kinetics. The apparent activation energy lpar;E rpar;, enthalpy lpar;▵ H rpar;and entropy lpar;▵ s✶lpar; of activation are 23.630 KJ mol 18.390 kJ mol-1and -225.95 J mol-1k-1respectively.