The invention discloses a water-soluble degradable quenching agent which consists of the following raw materials, by weight: 2-6 parts of alcohol, 4-8 parts of rhamnolipid, 6-10 parts of citric acid, 2-4 parts of butyl hydroxy anisole, 8-12 parts of rapeseed oil, 11-17 parts of cyclodextrin, 6-10 parts of pine oil, 15-25 parts of acrylic acid, 7-8 parts of saccharose, 0.5-0.8 part of 2-thioketone-trihydroxymethyl benzothiazoline and 10-20 parts of shell powder. A preparation method for the water-soluble degradable quenching agent comprises the following steps of: firstly, dissolving citric acid, butyl hydroxy anisole and pine oil into alcohol to obtain a mixed solution; then, adding water into the mixed solution and transferring the mixed solution into a reaction kettle, cooling the mixed solution and adding rhamnolipid, rapeseed oil, cyclodextrin and saccharose into the mixed solution after reaction is ended, stirring for 10 minutes and standing to obtain a mixture; centrifuging the mixture, taking liquid supernatant after the mixture is centrifuged, adding acrylic acid, 2-thioketone-trihydroxymethyl benzothiazoline and shell powder into the mixture, uniformly stirring, heating, preserving the temperature, cooling, and sealing by use of paraffin oil, and thereby obtaining the water-soluble degradable quenching agent. The prepared quenching agent has relatively good water solubility, is ecologically degradable, and is small in environmental pollution.