Abstract: Thick-walled cylinders are widely used to contain the effects of internal explosion events such as demilitarization of munitions and explosive manufacture.Formulae for calculating elastodynamic stresses of monobloc thick-walled cylinder under transient loading,which contain roots of frequency eigen-equation of thick-walled cylinder,are very complex,and it is difficult to find the analytical roots.Simplified formulae for prediction of stress at the inner surface and outer surface of a thick-walled cylinder were obtained by finding the positive roots of frequency eigen-equation of thick-walled cylinder.Numerical results indicate that the relative error between the simplified formulae and the exact solution is less than 6% when the ratio of outer radius to inner radius is no more than 2.