Abstract: High density polyethylene(HDPE) and woodflour were used as raw materials, and maleic anhydride grafted polyethylene(MAPE) as compatibilizing agent, woodplastic composites were produced by compression molding process,and different antioxidants were added into the composites during the production. The thermooxidative aging test was conducted on different composites, then the composites with different ageing time were immersed in water at room temperature, the effects of thermooxidative aging on the water absorption of different composites were studied. The results showed that the water uptake behaviors of the aged composites still abided by the general rule for that by other materials, i.e, the composites will absorb water quickly at the first stage, and then reach equilibrium; and more water will be taken by the composites with the prolong of aging time. Effects of different antioxidants on the water uptake behaviors of the composites differ from one another.