Abstract: Objective To discuss the applicability of internal standard in determination of cyclamate in wine by HPLC-tandem mass spectrometry. Methods After dilution wine sample was determined by HPLC-tandem mass spectrometry and quantified by external and internal standard methods respectively. Results The results by the 2 quantitation methods differed 11.2% in average, and the maximum relative deviation was 16.2%. And the result by external standard quantitation method proved to be consistent with that by the international standard GB/T 5009.97-2003. Conclusion The difference in results is thought to originate from matrix effect in HPLC-tandem mass spectrometry and the improper internal standard compound applied.