Abstract: A method for determination of 18 illegally added antiviral drugs, including metformin hydrochloride, penciclovir, oseltamivir phosphate, peramivir trihydrate, zanamivir, ribavirin, abidol, faviravir, lopinavir, ranimivir, amantadine hydrochloride, rimantadine hydrochloride, mabaloxavir, ritonavir, acyclovir, ganciclovir, famciclovir, and valacyclovir hydrochloride in herbal tea by liquid chromatography-tandem mass spectrometry was proposed. 1.000 0 g of herbal tea sample was taken and placed in a 50 mL-volumetric flask. 40 mL of the mixed solution of methanol and acetonitrile at a volume ratio of 1∶3 was added, and the solution was sonicated for 30 min and cooled to 25 ℃. The mixture was made its volume up to 50 mL with the mixed solution of methanol and acetonitrile at a volume ratio of 1∶3. The mixture was passed through a 0.22 μm nylon filter membrane, and the filtrate was used for determination. Waters ACQUITY BEH HILIC column was used as the stationary phase and the mixed solution composed of 10 mmol·L^-1 ammonium acetate solution containing 0.1% (volume fraction) acetic acid and acetonitrile solution containing 0.1% (volume fraction) formic acid at different volume ratios was used as the mobile phase for gradient elution. Electrospray ion (ESI) source was used for mass spectrometry and the targets were analyzed by multiple reaction monitoring (MRM) mode in positive ion (ESI⁺) scanning mode. Working curves were drawn with the matrix matching mixed standard solutions. As shown by the results, linear relationships between the corresponding chromatographic peak areas and mass concentrations of 18 illegally added antiviral drugs (salt antiviral drugs were calculated as free state) were kept in definite ranges, with detection limits (3S/N) in the range of 0.005-2.0 mg·kg^-1. Test for recovery was made by the standard addition method, giving results in the range of 70.3%-115%, with RSDs (n=6) of the determined values less than 12%. This method was applied to analysis of 387 batches of herbal tea samples, and amantadine was detected in 10 batches of herbal tea, with detection amounts of 0.125-420 mg·kg^-1. Metformin was detected in 4 batches of herbal tea, with detection amounts of 177-6 404 mg·kg^-1.