The paper deals with the bending properties of bamboo-wood composite plywood in five hygrothermal conditions, including normal condition (20 ℃, 65%), frozen (-55 ℃, 4 h), drying (150℃,4 h), cold water (20 ℃, 24 h), hot water (90～C, 4 h). The results showed that modulus of elasticity and modulus of rupture of this material treated under-55 ℃, 4 h was the best among the five hygrothermal conditions, increasing up more 130%, while that of this material treated in drying 150 ℃, 4 h; cold water 20 *C, 24 h; hot water 90 ℃, 4 h decreased compared with that treated in 20℃, 65%. After being tredated in drying and cold water, the render ratio of MOE was better than the render ratio of MOR, though the render ration of MOE was worse than the render ratio of MOR in hot water. The curve of loading and delection showed that bamboo and wood composite plywood mainly showed low-temperature brittleness and hot brittleness when treated in cold water, frozen condition, and drying. Hot water increased the viscoelastic property of bamboo wood composite plywood.