The invention discloses preparation of a high-molecular construction formwork material. The material is prepared by the following components: isotactic polypropylene, polyvinyl chloride, a reinforcing agent, a stabilizing agent, a foaming agent, an anti-oxidant, stearic acid, and a plasticizer. The invention discloses an application of the construction formwork. The construction formwork comprises a plate body, the thickness of the plate body is 10-25mm, and the plate body has a hollow structure; the plate body is internally provided with a primary support, and the primary support is in sawtooth shaped; one side of the plate body is provided with holes, diameters of the holes are 0.6-1.5cm, and the intervals between holes are 10-30cm; ribs are arranged at the side of the holes, the spaces between the ribs are 20-50cm, the ribs can effectively prevent deformation of the plate body, and the ribs have hollow structures; the ribs are internally provided with secondary supports, and the secondary supports are in V shaped. The high-molecular construction formwork material has the advantages of energy saving and environmental protection, complete recovery and utilization, resource saving, multiple usage frequencies, and long usage period; and construction formwork prepared by the material has the advantages of simple structure, easy splicing, and good resistance to impact.