Abstract: The adsorption mechanisms of the C7H7SH on the pure, defective and Hg/Pd doped graphene (G) surfaces were investigated using density functional theory (DFT). Two kinds of models are considered, Case 1: the C7H7SH was in parallel lying on various G surfaces; Case 2: the C7H7SH vertically placed on the various G surfaces and -SH was closed to these surfaces. The investigation revealed that the initial configuration of C7H7SH affected the interactions to some extent. There were the larger adsorption energies in the Case 1 than Case 2. Furthermore, the results of adsorption energies obviously displayed that the C7H7SH could be bound to defective and Hg/Pd doped G surfaces more tightly than the pure G surface in the Case 1, which was in agreement with the results of the density of states (DOS), and the deformation electron density.