Abstract: The stress-strain data of polyurethane was obtained by using the Hopkinson pressure bar test, which was used to analyze the Zhu-Wang-Tang（Z-W-T） constitutive model. And the elastic modulus, elastic constant and relaxation time were then identified. The results show that the model can better express the stress-strain relationship of polyurethane material in the range of true strain from 0 to 0.1.The stress attenuation characteristics of the polyurethane were studied, by which the stress attenuation coefficient was got as-0.45. The overall assembly structure of the projectile was used for the high overload simulation in the cannon, by which the stress attenuation equation was then verified. The results show that the relative error is less than 10%, and the double buffer protection can attenuate the maximum stress amplitude of the circuit board by 30%. According to the simulation results, in the length direction of the circuit board, 0 cm-1.8 cm close to the bottom of the circuit board at the tail of the projectile will experience a larger stress, while the rest of the position will experience a smaller one. All the research above provided a basis for protection under high g impact.