The invention discloses a method for preparing a composite light-weight wallboard by utilizing nonmetal materials of waste electronic circuit boards. The method comprises the following steps that: cement and the nonmetal materials of the waste electronic circuit boards are used as main raw materials, wherein, the grain sizes of the nonmetal materials are 10 to 400 meshes; the main raw materials, fly ash, light aggregate, additives and water are evenly stirred and mixed to prepare a core material; then the core material is poured into a mould on which external panels are well placed, and is filled between the two external panels; concave-convex grooves are combined with side surface bevel edge structures; and through condensation, maintenance and then demoulding, the composite light-weight wallboard is obtained. The external panels of the wallboard have good stability and high strength, the novel energy-saving light-weight core material is combined between the external panels, and the preparation raw materials have the advantages of wide source, low cost and environmentally protection, so the wallboard has the characteristics of light weight, high strength, energy conservation and heat preservation, and simultaneously has good mechanical, thermotechnical, sound-insulation, fireproof and durable performance.