Abstract: In this study, a method for the determination of morphine, codeine, nacodine, papaverine and tibain residues in catering crayfish by ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was established. After preparation of crush and mixture, the samples were stirred and dispersed with 0.1 mol/L hydrochloric acid solution and ultrasonic treated for 30 min, then extracted with acetonitrile and QuEChERS powder (6 g anhydrous magnesium sulfate and 1.5 g anhydrous sodium acetate). After centrifugation, the supernatant was pipetted for analysis. The chromatographic separation conditions were as follows: Stationary phase was used ACQUITY UPLCTM BEH HILIC chromatographic column (1.7 μm, 2.1×100 mm). The mobile phase of gradient elution was composed of acetonitrile and 10 mmol/L ammonium formate containing 0.1% formic acid, respectively. The target compounds were analyzed and quantified via electrospray ionization (ESI⁺) mode ionization and multiple reaction monitoring (MRM), and 9 kinds of commercial crayfish were selected as samples for inspection. The results showed that the linear range of internal standard method for quantitative analysis of morphine and codeine was 5~250 ng/mL, and that of external standard method for quantitative analysis of papaverine, nacodine and tibain was 1~50 ng/mL. Within the linear range, the correlation coefficient between peak area and injection concentration (ng/mL) was greater than 0.995. The detection limits and the limits of quantitation of five alkaloids were 0.6~3.7 μg/kg and 2.0~12.4 μg/kg, respectively. The averaged recoveries (n=6) were 80％~110％ and the relative standard deviations (RSDs) were below 10%, and the papaverine and other 5 components were detected in 9 commercial samples. The method was suitable for the qualitative and quantitative analysis of five alkaloids, and was fast, simple, and sensitive.