Reconstituted bamboo Lumber suffers surface and mechanical properties degradation after exposure to outdoor environment. In this paper, Neosinocalamus affinis bamboo bundles was selected to thermo-treated at three temperature levels (160,180 and 200°C) for 2 hours and investigated the effect of xenon-arc light irradiation with water spray on the changes in color, thickness and mechanical properties of reconstituted bamboo lumber. The results indicated that the surface color of the samples changed rapidly during the irradiation process and the change rate decreased as the increasing of thermo-treated temperature. The mechanical properties analysis indicated that MOE wasn’t much affected by the thermo-treated and artificial weathering test, whereas MOR and shear strength decrease after exposure. The thickness swelling after exposure was improved by the thermo-treatment and decreased as the treated temperature increased.