Abstract: Adsorption properties of thiophene and methylthiophenes on the unsaturated Mo site of MoS2 cluster were investigated by the first-principle DFT calculations. The calculated results indicate that the thiophene compounds prefer to lie on the top two Mo atoms of Mo16S32 cluster. The adsorption ability of thiophene compounds on the Mo16S32 cluster is 2,3-DMT>3-MT>3,4-DMT>2,4-DMT>TP>2-MT>2,5-DMT. The results indicate that thiophene with one methyl substituent in 3- position is beneficial to adsorption, but methyl in 2- position is not conducive to adsorption. When two positions on thiophene are substituted, the adsorption energy decreases as the distance of the two methyl increases. According to the bond length, Mayer bond order and Mulliken population analysis, the C-S bond length and bond order of the adsorbed thiophene is up and down, respectively after adsorption. The electrons in the hybridized orbitals of adsorbed thiophene ring transfer to Mo atoms, and the electrons in the 4dx2-y24dxy4dz2 atomic orbitals of Mo atom transfer to antibonding orbital of thiophene ring. It benefits for the thiophene rings activation and subsequent electrophilic hydrodesulfurization reaction.