The invention discloses a method for detecting the residual quantity of sodium nifurstylenate in an aquatic product, which comprises the following steps: dispersing a sample by using formic acid, taking tert-butyl hydroxy anisole as a protective agent, extracting by using acetonitrile, precipitating protein by using potassium ferrocyanide and zinc acetate, purifying by using normal hexane and a C18 column, concentrating under reduced pressure under an alkaline condition, determining by using a liquid chromatography-tandem mass spectrometer, and qualitatively and quantitatively analyzing the residual quantity of the sodium nifurstylenate in the sample.