Molecular dynamics simulation is applied to investigation of energy exchanges during hydrogen collision with graphite sheet containing a vacancy. The effects of the monovancancy defect on the energy exchanges are discussed in detail. This paper analyzes the energy loss of the incident hydrogen atom, the energy range for the adsorption process, and the energy transfer process for target atom, in the course of a hydrogen atom bombarding the carbon atom at the edge of monovacancy defect in the graphite sheet. The simulation results show that the adsorption process proceeds more easily when the graphite sheet contains a vacancy than when the graphite sheet has perfect crystalline structure. In certain areas of the graphite sheet, adsorption of an incident hydrogen atom can occur in two energy ranges. The sp2 structure as well as overhang configuration occurs when a hydrogen atom is adsorbed. This adsorption process does not reduce the C—C bond energy. It is found that the carbon atom at the edge of monovacancy defect can adsorb an incident hydrogen atom more easily but can not diffuse the gained energy as efficiently as in a perfect graphite sheet. These results are helpful for understanding the chemical erosion of carbon based materials and the ensuing tritium retention in fusion devices.