The invention discloses a method for simultaneously detecting the contents of three alkaloids in a lycoris plant, which is capable of quickly extracting and qualitatively and quantitatively analyzingalkaloid matters of galanthamine, lycoramine and lycorine in the lycoris plant. According to the method disclosed by the invention, gradient eluting is carried out by taking an LC (Liquid Chromatography)-MS (Mass Spectrometry) technology as the basis, analysis is carried out in an MRM (Multiple Reaction Monitoring) mode under positive ion scanning by connecting LC with tandem MS, the three alkaloid matters in the lycoris plant can be quickly extracted and accurately, qualitatively and quantitatively analyzed, the analysis time can be shortened to a large extent, the analysis accuracy is increased, a detection result can be obtained within a program time which is not more than 6.0 minutes, the retention time of the three alkaloids is within 3 minutes, the adding standard recovery rate is 97.2 to 100.2 percent, the RSD (Relative Standard Deviation) is 0.8 to 4.3 percent, and the analysis speed and the analysis accuracy are greatly increased; an effective and accurate analysis method is provided for researching an accumulation law and constructive metabolism regulation of the three alkaloids in the lycoris plant.