The invention relates to a preparation method of special polyvinyl chloride resin for chlorination. The method comprises the following steps: uniformly premixing a quality agent and vinyl chloride monomer in advance, adding deionized water, a dispersing agent I, a dispersing agent II, a PH regulator, a heat stabilizer, a chain transfer agent and an initiator into a polymerization reactor to perform polymerization reaction, ensuring that the quality agent adopts water soluble polyvinyl alcohol with low polymerization degree and low alcoholysis degree, and the dispersing agent I adopts grafted polyvinyl alcohol copolymer resin, and adopting special production technology to premix the quality agent and the vinyl chloride monomer in advance. The special polyvinyl chloride resin for chlorination, prepared through the method, has the advantages that the particle surface films are less or no film exists, the resin particle shapes are regular, the structure is loose, pore distribution is uniform, the degree of concentration of resin particle sizes is high, polymerization reaction is stable during production, and the quality repeatability of all batches of resin is good, and the special polyvinyl chloride resin is particularly applicable to the preparation of chlorinated polyvinyl chloride resin through chlorination.