Safety countermeasures have been implemented in nuclear power plants in Japan under the new nuclear regulation. The importance of structural integrity of components which are attacked by tornado missile has been growing as one of the countermeasures. In the case of impact analysis for tornado missile, strain rate dependency needs to be considered in the stress strain relationship, which is different from static analysis. However, it is difficult to obtain the data of stress strain relationship which strain rate is over 103 s−1 due to the restriction of test equipment. Therefore, a new method to estimate strain rate dependency of stress strain relationship on the high strain rate condition was developed. An inverse analysis using the deformation data obtained by the Taylor impact test and FEM analysis was applied in the method. Stress strain relationship estimated by the method was verified by comparing it to Split Hopkinson Bar (SHB) test result. It was confirmed that the method could estimate strain rate dependency of stress strain relationship accurately.