The critical impact velocity range was obtained by using the updown method in the fragment impact experiments. In the numerical simulations, the mechanical damage and ignition reaction of the charge were depicted by the node tiebreaking method and the thermoelasticplastic material model with the chemical kinetics equation. The experimental results are in agreement with the simulated ones. So the node tiebreaking method and the thermoelasticplastic material model with the chemical kinetics equation can be used to effectively simulate the ignition of explosives under fragment impact.