Influences of water absorption on Charpy impact value for composite polymers, which are aluminum powders dispersed nylon6 samples, have been investigated. Although the aluminum dispersion from zero to 40 vol%Al decreases the impact value, the water absorbing treatment for 10⁵ s at boiling point largely increases the impact values of all composite polymers. It is explained that water molecules in nylon6 mainly relax the impact force.