The invention relates to a method for producing a polyvinyl chloride resin special for a battery separator with moderate polymerization degree, which comprises the following steps: respectively adding demineralized water, chloroethylene, a dispersing agent, an initiator, a pH value regulator and an auxiliary agent in a closed polymeric kettle to carry out polymerization at a stirring rotating speed of between 95 and 240rpm at the temperature of between 45 and 53 DEG C; regulating downward the stirring rotating speed to 0.41 to 0.55 time of the initial rotating speed when the polymerization conversion rate is between 6 and 15 percent; when polymerization pressure is reduced to 0.26 to 0.30 MPa, adding a terminating agent into the closed polymeric kettle to finish the polymerization, wherein the reaction time is between 6 and 9 hours; and carrying out gas stripping, centrifugation, steam flow drying, cyclone drying on slurry and allowing the slurry to pass through a bag-type dust collector to obtain the polyvinyl chloride resin finished product special for the battery separator with the moderate polymerization degree. The resin has the moderate polymerization degree and moderate structural porosity. The average grain diameter of the particles of the resin is less than 40mu m. The resin has concentrated particle size distribution and uniform and regulated particles. The adsorption rate is between 16 and 24 grams per 100 grams of resin. The apparent density is between 0.40 and 0.52g/ml. The production process and the formulation are reasonable and meet the requirements of the production field of the battery separator.