The invention discloses a composite board made from waste plastics and fly ashes and a method for producing the same. The composite board is prepared from the waste plastics and the fly ashes according to certain weight ratio. The main raw materials for producing the composite board comprise the waste plastics and the fly ashes, wherein the waste plastics are discarded in industrial production and in human life and comprise waste polypropylene plastic, waste polyethylene plastic, waste polystyrene plastic and waste polyvinyl chloride plastic and the like, and the fly ashes are discharged by coal-fired power plants and the chemical industry; the main raw materials are manufactured into the composite board through crushing and hot pressing; the manufactured composite board meets the national standards for construction templates, not only reduces the environmental pollution caused by industrial fly ashes and plastic wastes, but also can be applied to replacing wooden construction templates or steel construction templates widely used in the prior building operations, and not only has the advantages of low production cost, light weight, high strength, impact resistance, and easy demoulding, but also 'turns harmful into beneficial and changes waste into valuable', and significantly speeds up the process of recycling wastes in China.