Abstract: VG(void growth) damage model is generalized to the 2D situations, which counts in the effect of the principal stress direction on the evolution of damage, and is used in the 2D numerical simulations of spallation of steel tube driven by sliding detonation of high explosive GI-920, as well as the explicit fracture algorithm. The different pressure profiles on the outer surface of steel tube between the 1D implosion case and the 2D sliding detonation case are analyzed. Especially the influence of the thickness of high explosive on the pressure profiles is investigated in detail. The numerical results present the distribution and evolution of damage in the steel tube, as well as the initialization and extending of the spalled crack. The initial thicknesses of spalled layer obtained numerically conform to the experiments.