•Bamboo charcoal (BC) was used as reinforcing filler of wood-plastic composites.•BC could have strong interfacial interaction in the wood-plastic composites (WPCs).•The BC-WPC composites displayed lower water absorption properties.•The BC-WPC composites displayed higher flexural, tensile and thermal properties.In order to enhance the mechanical properties and thermal properties of wood plastic composites (WPCs), bamboo charcoal (BC) was used as reinforcing filler of WPC, and a series of BC-WPC composites were prepared. The effect of BC and water treatment on water absorptions, morphologies, mechanical properties, the effect of water treatment on mechanical properties and thermal properties of the composites were investigated. The results showed that BC could have strong interfacial interaction in the WPC. The water resistance, flexural properties, tensile properties and thermal properties of BC-WPC were higher than WPC. The flexural and tensile properties were reduced and the impact strength was increased after water treatment. The presence of BC resists the influence of water absorption on composites mechanical properties.