The invention relates to a method for rapidly determining 
xylanase in 
fermentation liquor. The method comprises the following steps: centrifuging 1000*g of 
fermentation liquor for 10 minutes, taking the supernatant, determining the activity of 
xylanase, and preheating properly diluted supernatant, 10g / L of 
xylanase solution and 50mM of 
sodium phosphate buffer solution with the pH value of 7.0 at the temperature of 39 DEG C for 15-30 minutes, adding 75micronL of 
sodium phosphate buffer solution and 50 micronL of xylanase solution into 75micronL of diluted supernatant, reacting at the temperature of 39 DEG C for 15-30 minutes, adding 300micronL of DNS solution and ending the reaction; heating in a boiling water bath for 5 minutes, and cooling to 
room temperature; putting 200-300 micronL of solution on a dried and clean 96-pore ELISA plate, detecting a light absorption value at 530-550nm by using a full-automatic 
microplate reader, and calculating the activity of xylanase according to a 
standard curve of 
xylose. According to the technology, a method for measuring the xylanase in the 
fermentation liquor is revised, the activity of the xylanase can be rapidly, greatly and accurately measured, and personal errors are reduced. Meanwhile, fewer samples can be detected.