Volatile fatty acids (VFA) are important control indicators for anaerobic fermentation reactions, and it is necessary to determine an accurate, precise, simple and fast test method. In the experiment, GC-122 gas chromatograph, N2000 chromatography workstation, organic carrier 402 as packing material, and FID as detector were used to determine the VFA in the anaerobic fermentation broth sample after formic acid pretreatment under the conditions of column temperature of 200°C and carrier gas (N2) flow rate of 52.0 mL/min. The results show that the separation effect of this method is good, the recovery rate of each component is between 94%~108%, the coefficient of variation is less than 3%, the repeatability is good, and the test time is short.