The invention discloses a preparation method of polyvinyl chloride. The method comprises the following steps: S1: preparation of aid liquid: adding a dispersing agent and an initiator into a solvent water, wherein the dispersing agent comprises 88%-alcoholysis-degree polyvinyl alcohol which accounts for 0.270-0.300 wt% of the solvent water, 72%-alcoholysis-degree polyvinyl alcohol which accounts for 0.225-0.335 wt% of the solvent water and 50%-alcoholysis-degree polyvinyl alcohol which accounts for 0.113-0.138 wt% of the solvent water, and the initiator is di(2-ethylhexyl) peroxidated pyrocarbonate which accounts for 0.850-0.875 wt% of the solvent water; S2: adding the aid liquid and a vinyl chloride monomer raw material into a polymerization kettle, and carrying out polymerization reaction; and S3: when the polymerization reaction finishes, adding a terminator into the polymerization kettle. By determining the raw material proportioning and the technical process and parameters in the polyvinyl chloride preparation method, the process of producing the polyvinyl chloride resin in the polymerization kettle has the advantages of higher smoothness and shorter reaction time; and the properties of the prepared polyvinyl chloride resin product are more excellent.