A simple, effective and suitable UFLC-ESI-MS/MS method was developed to simultaneously determine five characteristic alkaloids (piperine, piperlonguminine, Aα,β-dihydropiperlonguminine, pellitorine and piperanine) in Piper Iongum L.The alkaloid contents of Piper nigrum L.and P.Iongum L.were compared.The analysis was carried out in multiple reaction monitoring scan mode.The method showed good specificity, linearity (R2 > 0.995), stability (RSD < 2.53%), repeatability (RSD < 2.58%)and recovery (90.0%-103.5%).The limit of detection and limit of quantitation of the five alkaloids were in the range of 0.02-0.03 and 0.05-0.10 ng/mL, respectively.The intra-day and inter-day variations were less than 9.30% and 9.55% respectively.The validation results confirmed that the method could simultaneously determine the target alkaloids in the sample.Furthermore, the identities of the alkaloids were verified by HPLC-ESI-MS/MS.Compared with P.nigrum L., P.Longum L.had lower piperine content but was enriched in the other four alkaloids.