Abstract: Based on the data of Drop-weight test of various kinds of specimens with different thickness, it could be concluded that the value of T_NDT is not only dependent on the materials but also the thickness of the specimen. The relationship between T_NDT and thickness could be described by a function of: T_NDT=At^-m+B, where A、B、m are coefficients related with the materials. Therefore, the six type of specimens (P1~P6) with thickness 12~50mm and their test conditions are recommended in engineering design in which the failure characteristic of materials should be properly described for the reliability of the design.