Since the discovery of the Haversian system in human bone over three hundred years ago, researchers have been wondering about its mechanical advantages. Despite positive experimental evidences on the intervention of Haversian systems in the fracture process, the contributions of Haversian systems to bone fracture have been obscure. Here a unique microcracking process accompanying the inelastic deformation of Haversian bone is reported that may shine light on its structural advantages over other bones. When compressed transversely, the concentric bone lamellae surrounding each Haversian canal allow multiple radial microcracks and arc-shaped cracks to develop intralamellarly. Groups of circumferential arc-shaped microcracks develop in high shear zones and radiate out in oblique directions from each Haversian canal. At the cortical bone level, where the Haversian systems are randomly distributed within the interstitial matrix, multiple nucleations and stable development of such arc-shaped cracks happen to most Haversian systems progressively. As a result, Haversian bone is not sensitive to the presence of Haversian canals and demonstrates high inelastic strains at macroscopic level.