Abstract: The present invention discloses a plastic composition, a composite floor including the plastic composition and a preparation method thereof. The plastic composition is prepared from the following components in parts by weight: 30-55 parts of polyvinyl chloride, 35-55 parts of limestone powder, 0.5-5 parts of polyurethane foaming agent and 0.5-5 parts of stabilizer. The composite floor includes a decoration layer and a supporting layer, wherein the supporting layer is prepared from the plastic composition. The composite floor provided by the present invention has the advantages of simple structure, beautiful and elegant appearance, and good anti-water, anti-insect and anti-mildew effects. Moreover, the composite floor can effectively save wood resources, is low in cost and is more environmentally friendly.