A manipulation probe and an atomic force microscope (SFM) tip was used to investigate the mechanical behavior of a single silicon nanowires (SiNW) under bulking and bending conditions. The results show that under a homogeneous strain, the NW would become semicircular at the maximum deformation and its value is found to be ca. 1.5%. An increase in critical load, which is defined as the load higher than a clearly non-linear and bulking deformation, cause the NW to buckle. The mechanical behavior of the NW is found to be same as in the small-deflection linear part, showing that linear regime of the NW is rather large. The results also show that the degree of bending of SiNW is determined by the thickness of the object rather than its aspect ratio. The SiNW are also found to show ultrahigh flexibility and strong toughness, while the mechanical behavior of NW is found to follow Hooke's Law.