The invention relates to a method for preparing a CPVC resin filling agent by adopting ardealite, and in particular to a method for preparing the CPVC resin filling agent from ardealite serving as a raw material. The method for preparing the CPVC resin filling agent by adopting the ardealite comprises the following steps: reacting the ardealite subjected to impurity removal with sodium carbonate, and obtaining calcium carbonate; performing anaerobic fermentation on the obtained calcium carbonate, potato pulp, alpha-amylase and soybean dregs under the action of lactic acid bacteria to obtain lactic acid; performing an esterization reaction on the obtained lactic acid and stearic acid under the action of protection gas, performing a neutralization reaction on stearic acid lactyl acid obtained by the esterization reaction and a sodium carbonate and calcium carbonate mixture, and preparing sodium stearyl lactate and calcium stearyl lactate; preparing CPVC resin from a mixture of the sodium stearyl lactate and the calcium stearyl lactate, which serves as a filling agent.