The invention relates to a preparation method of a PVC (polyvinyl chloride) composition, relating to the technical field of production of PVC granules. The preparation method comprises the steps of uniformly mixing PVC resin powder, environment-friendly plasticizer, organic silsesquioxane, stearic acid and an antioxidant, extruding with a double screw extrusion machine for granulation to obtain the product. The feeding amounts of the PVC resin powder, the environment-friendly plasticizer, organic silsesquioxane, stearic acid and the antioxidant are 30-95%, 0-69.2%, 0.1-30%, 0.5-1% and 0.2-0.6% of the total mass of the fed materials. The PVC composition and the preparation method of the PVC composition provided by the invention do not need other organic salt stabilizers. In case of preparing rigid PVC, other types of plasticizers are also not required. In addition, as organic silsesquioxane is a nanomaterial containing an organic group, organic silsesquioxane is easy to disperse in PVC, and the material keeps transparency all the time after being processed for many times.