Abstract: Using Monte-Carlo method, the electon transport and energy deposition in material are calculated. Combining with the elastic plastic hydrodynamic equations, numerical results cover the thermal mechanical effect and the blowoff impulse on Ly-12 Al induced by irradiating of the impulsive electrobeam which caused by ‘FLASH Ⅱ’-an impulsator of relativistic electron beams. these results are compared with the experimental data.