The invention relates to a wood-plastic composite material which is prepared by waste-old plastic mixture and a process for preparation, which relates to a wood-plastic composite material and a process for preparation. The invention solves the problems that the mechanical properties of the wood-plastic composite material which is prepared by the existing waste-old plastic mixture are bad and the like. The wood-plastic composite material is prepared by wooden fiber material, modified waste-old plastic blend and lubricating agent. the process for preparing comprises preparing modified waste-oldplastic blend, and then mixing the wooden fiber material, the modified waste-old plastic blend and the lubricating agent, and further adopting a continuous extrusion modeling technique, at last, getting wood-plastic composite material. Compared with the prior art, the bending strength of the wood-plastic composite material of the invention is improved by 30%-60%, and the impact strength is improved by 58%-140%. The process for preparing the wood-plastic composite material of the invention not only has simple technique and high production efficiency, but also reinforces the interface combination of the modified waste-old plastic blend and wooden fiber material, and the invention improves the mechanical properties of wood-plastic composite material.