Most naval architects are now very interested in the mechanism of fast fracture (brittle crack propagation) and crack arrest from the viewpoint of dynamic fracture mechanics. The concept of crack arrester design for steel structure has been based on static approximation. Recently the behavior of fast crack is being more and more clarified by numerical approach using big computor. In the previous paper, three types of brittle fracture propagation-arrest test were conducted and it was revealed that dynamic fracture toughness in ship steel is dependent on temperature and crack velocity, and the behavior of brittle crack propagation and arrest in double tension test are quite different from those in DCB test. This paper gives the results of an experimental investigation of two different size double tension tests which were conducted to see how the reflected stress waves from boundary affects the behavior of running crack. Further a crack arrester design procedure is discussed with a focus on energetics aspect of the crack propagation process.