Abstract: During the thermal enhanced oil recovery (EOR) process, the existence of H₂S among the produced gase brings great trouble to petroleum exploration and development. Four model compounds of heavy oil (2-methylthiophene, BBT, DBT, and thianthrene) were carried out to study the pyrolysis process of different types of sulfur containing organic compounds and the catalysis of aluminum ions. The results showed that the pyrolysis reaction of 2-methylthiophene, benzothiophene, dibenzothiophene and thianthrene wouldn't occur under the reaction temperature of 280 ℃. Due to the different electron cloud density of the S atom, the production of H₂S is in order of 2-methylthiophene >benzothiophene>dibenzothiophene>thianthrene. Al³⁺ had a catalytic effect on the model compound. The aquathermolysis path of four kinds of model compounds was discussed. The results indicated that the secondary hydrolysis plays an important role in the process of generating H₂S by aquthermolysis. In the presence of oxygen, aldehydes were first oxidized to carboxylic acids instead of generating CO by aquathermolysis.