This study deals with the mechanical behaviour in bending and the anatomical changes under several deflection rates. Sugi (Cryptomeria japonica D. Don) wood was used in the test, and the four-point bending method was adopted. The sizes and dimensions of test specimen were 2cm(R)×2cm(T)×32cm(L). Microscopic observations were carried out with the filmy replica method and the SEM (Scanning electron microscopy). The mechanical properties of wood are affected by variation of the deflection rate. The MOE, modulus of elasticity, and the value ofσ_p/MOR, proportional limit by modulus of rupture, increased linearly with logarithm of deflection rate. With increasing deflection rate, the microscopic failures in tracheids after ultimate decreased. In water-saturated wood, more microscopic compression creases observed than air-dried wood. It is believed that the variation of mechanical properties due to deflection rates are closely related to the variation of microscopic compression creases of wood.