A desensitizing mechanism of graphite in explosives versus mechanical stimuli was investigated using computational methods including density function theory and molecular dynamics. Dependences of energy change versus compression ratio and internal stress versus compression at absolute zero degree showed that the most possible compression was along the c-axis of graphite crystal. The result of molecular dynamics at room temperature indicated that the slide can readily occur between neighbor layers, but the distance between them can hardly change. The calculated potential energy of the slide of graphite within 0-0.19 kJ/cm(3) is much larger than the potential energy of compression of common explosives to the extent of no detonation, for example, HMX, 0-0.046 kJ/cm(3). It implied that the kinetic energy induced by mechanical stimuli can easily and partly convert into the potential energy of the slide and prevent explosives from forming hot spots. This should be the root reason for graphite used as a desensitizer in explosives.