The invention provides a feed-in hazardous waste diluting method for an incinerator. In a process that propylene dichloride is used as a raw material to produce tetrachloroethylene, produced heavy-constituent waste comprises carbon tetrachloride, tetrachloroethylene, hexachloroethane, hexachlorobutadiene and hexachlorobenzene; and in a refining process that propylene dichloride is used, produced light-constituent waste comprises chloropropane ether, trichloropropane, 2-methyl-2-pentenal, 1-chloro-2-propanol, 2-chloro-1-propanol and 3-hexenal. Carbon tetrachloride is separated from the heavy-constituent waste through a vaporizer, and the left heavy-constituent waste and the light-constituent waste are mixed, so that a diluted material is obtained. The invention further provides a feed-in hazardous waste diluting device for the incinerator. According to the method and the device, the heavy-constituent waste can be prevented from solidifying and blocking pipes in a conveying process; furthermore, sufficient burning of the waste can be guaranteed; and hexachloroethane is prevented from decomposing at a high temperature and producing hypertoxic phosgene.