Using the closed orbit theory, we studied the photodetachment cross section of H- in a microcavity, which is made of two parallel metal and elastic surfaces. The results show that both the upper and lower surfaces of the microcavity have great influence on the photodetachment cross section of H-. If we fix the distance between the metal surface and H-, when the distance between the elastic surface and H- is large, the influence of the elastic surface on the photodetachment cross section is small. The oscillation amplitude and the oscillation frequency of the cross section approach to the case of the photodetachment of H- near a metal surface. With the decrease of the distance between the elastic surface and H-, the oscillation amplitude is increased and the oscillation frequency is decreased. If we fix the distance between the elastic surface and H-, with the increase of the distance d0 between the metal surface and H-, the influence of the metal surface is decreased. When the d0 is increased to 500 a.u. the cross section approaches to the case of the photodetachment of H- near an elastic surface. So we can change the distance between the upper and lower surface of the microcavity to control the photodetachment of H-. This study provides a new understanding on the photodetachment process of H- in the presence of surfaces and microcavity.