The invention aims at overcoming the defects in the prior art, and provides a desizing agent with the advantages that the desizing effect is good; the damage on fabrics is small; the treated fabrics have a good wool effect, hand feeling and whiteness; in addition, the seepage performance and the dispersion performance are good; the refining effect is achieved. The invention provides the desizing agent, which is prepared from the following ingredients in parts by weight: 2 to 8 parts of sodium hydroxide, 15 to 20 parts of nonylphenol polyoxyethylene ether, 5 to 10 parts of dodecyl trimethyl ammonium chloride, 5 to 10 parts of glyceryl cocoate, 2 to 7 parts of coconut acid monoisopropanolamide, 6 to 12 parts of isocetyl stearate, 1 to 3 parts of polydimethylsiloxane, 2 to 6 parts of sodium laurate, 4 to 8 parts of glycol, 1 to 4 parts of polyvinylpyrrolidone, 2 to 6 parts of ammonium persulfate, 1 to 4 parts of potassium chloride, 1 to 4 parts of nano-zinc oxide, 2 to 5 parts of ethylhexyl palmitate, 8 to 15 parts of propyl alcohol and 25 to 35 parts of water. The desizing rate of the fabrics treated by the desizing agent provided by the invention is 96.1 percent or higher; in addition, the fabrics cannot be damaged.