Abstract: HPLC with QAMS was applied to the determination of 3 acetophenone compounds, i.e., 2,4-dihydroxyacetophenone, 2,5-dihydroxyacetophenone and baishouwu benzophenone in sample solutions of Cynanchum bungei Decne before and after fermentation. Sample solutions of Cynanchum bungei Decne before and after fermentation were prepared. In HPLC analysis, Thermo C₁₈ chromatographic column was used as stationary phase and mixtures with various ratios of water (A), CH₃CN (B) and CH₃OH (C) were used as mobile phase in the gradient elution, and the 3 analytes mentioned above were well separated by this process, with their peak areas measured by DAD at the same wavelength of 265 nm. Contents of the 3 analytes were calculated separately by QAMS and external standard method. It was shown that results found by the 2 method were in high consistency and it was concluded that the use of QAMS in quality evaluation of the analytes in the sample solutions before and after fermentation of Cynanchum bungei Decne was feasible. 12 portions of the same of Cynanchum bungei Decne from same batch were collected and testing solutions of 6 portions without fermentation and other 6 portions with fermentation were prepared and analyzed by the procedure described above. As shown by the results, average values of contents of 2,4-dihydroxyacetophenone and 2,5-dihydroxyacetophenone in solutions of the fermented samples were higher than those found in solutions of non-fermented samples (i.e. 2,4-dihydroxyacetophenone raised from 0.208 mg·g^-1 to 0.235 mg·g^-1, and 2,5-dihydroxyacetophenone from 0.152 mg·g^-1 to 0.180 mg·g^-1) and average content of baishouwu benzophenone in fermented samples was found lower than that in non-fermented samples (i.e. from 0.678 mg·g^-1 lowered to 0.543 mg·g^-1). In addition, it was shown that the values of relative correction factor and relative retention time found for 2,5-dihydroxyacetophenone and baishouwu benzophenone with different contents were same on the whole, taking 2,4-dihydroxyacetophenone as reference.