The invention belongs to the technical field of composite material, in particular to environment protective plastic-wood composite material and a preparation method thereof. The environment protective plastic-wood composite material is prepared with the following raw material: waste polyethylene, wood fiber powder, coal ash, silane coupling agent, activated calcium carbonate, radiation sensitizer and lubricant. The plastic-wood composite material is characterized by the integrated recycling of waste, environment protection, energy saving and emission reduction, reusability, corrosion and mildew resistance, rain and sun resistance, low cost, applicability to industrial production and the like, can save a lot of wood resources, and facilitates environment protection.