In order to evaluate the characteristics of propagation and arresting of brittle crack in steel plates, flat-temperature type (isothermal) and gradient-temperature type Double Tension Test are widely earned out in Japan. In general different results are obtained from these two types of test. Nowadays it seems to be thought that flat-temperature type test is more essential and gradient-temperature type test is just a convenient method to save material consumption for testing. On the basis of energy considerations and effect of crack length, the authors investigated the results of those two types of test. They showed that both of them are identical in substance and the results of flat-temperature type test is thought to be arresting characteristics for shorter cracks. They conclude that conservative criteria for arresting phenomena are to be based on the arresting data corresponding to such a long crack that the length of the crack has no more effect and gradient-temperature type test is preferable in this respect if the cracks are arrested after propagating through sufficient length. Correlation between Double Tension Test and small size test (pressed-notch boundary Charpy test) is also discussed.