The object of this study is to compare the shock isolation characteristics of the commercially available rubber washers due to the difference in a tightening torque and hardness. Drop impact test using a steel ball which can simulate the pyroshock acceleration was devised. The test results show that silicon had the highest shock isolation performances followed by urethane, nitrile showed the least performances. In addition, the test results show that the smaller a tightening torque and hardness, the shock isolation characteristics are improved. And this study propose an analysis method using the shock transmissibility function in order to minimize some uncertainty of the impact excitation in the shock response spectrum analysis.