Objective To use desorption corona beam ionization-mass spectrometry for rapidly screening illegal synthetic drugs in weight reducing dietary supplements,and precisely quantifying the suspected sample by HPLC-UV.Methods The qualitative identification of illegal additives,i.e.,fenfluramine,phenolphthalein,sibutramine,N-di-desmethylsibutramine,N-mono-desmethylsibutramine in samples was performed by comparing MS and MS2 spectra of samples with standard substances by DCBI-MS.Accurate quantitation of these five targets was obtained by HPLC-UV.Results The concentration of targets was linear in the range of 0.25-300 mg/L.Three illegal synthetic drugs in three of twelve samples were detected by DCBI-MS.The re-detecting results of HPLC-UV showed that the semi-quantitative results of DCBI-MS were credible.Conclusion Using DCBI-MS and cooperatively with HPLC-UV in detecting illegal synthetic drugs in weight reducing dietary supplements is fast,high-throughput and high-precision.Sample pretreatment is unnecessary when the determination of multiple components with DCBI-MS method.The analysis time for one aliquot is less than 1 min.