It is a well-known fact that the surfaces can affect the photodetachment of negative ion. In this paper, we focus on how the photodetachment cross-section of H- is altered when it is placed near two perpendicular metal surfaces. We begin by briefly presenting the electrostatic image potential of the detached electron caused by the metal surfaces, then we study the classical motion of the photo-detached electron near two perpendicular metal surfaces. The photodetachment cross-section of this system has been derived and calculated based on the closed orbit theory. The results show that the cross-section depends on the photon energy and the ion-surface distances sensitively. Compared to the case of the photodetachment of H- near one metal surface, the oscillatory structure in the cross-section of our system becomes much more complicated. This study provides a new understanding on the photodetachment process of negative ion or atoms in the vicinity of surfaces or cavities. (C) 2011 Elsevier BV. All rights reserved.