Abstract: High-speed camera and optical microscope were used to study the fracture characteristics of the 45 steel cylinder and the effect of the heat treatment conditions on them. Results show that while the temper temperature rises, the intensity decreases and static fracture strain increases, the time of crack generation and resultant leakage in the outer surface of the 45 steel cylinder delays under detonation loading, at the same time the corresponding strain increases, the size of the fragment increases. The reason that the static mechanics characteristics and the dynamic fracture characteristic of the 45 steel are evidently different is that the buildup and the component of the materials microcosmic structure are greatly changed, i.e. static mechanics characteristic and dynamic fracture characteristic depend on the materials microcosmic structure.