Photodetachment of a negative hydrogen molecular ion near an interface is studied by using the two-centre model and the closed orbit theory. The calculation results show that the photodetachment cross section is related to the distance between the two centres in the H-2 and different molecular ion-interface distances. The comparison between the cross section of H-2 near an interface with the section of H- shows that at the equilibrium distance of two centres and at low photon energy, the photodetachment cross section of H-2 is about twice the cross section of H-, which shows that the interference of the two nuclei is very strong; when the distance between the two centres is large, the section of H-2 is almost the same as the cross section of H- near one interface, which indicates that the interference effect of the two centres vanishes.