Osteon is a fundamental unit of cortical bone. Osteons are elongated cylindrical structure and the directions are generally aligned with axis of long bone. It is considered that BMU movement leads to elongation of osteons. However, the reason why BMU moves along the axis of long bone remains unclear. In this study, from mechanical standpoints, we propose mathematical models of trabecular and osteonal remodeling combining mechanosensing and signaling systems, and analyze BMU movement in trabecular and osteonal remodeling. We found that continual resorption on the surface of high RANKL concentration, resulting from low stress, leads to BMU movement.