Plant protein beverage adulteration occurs frequently, which may cause health problems for consumers due to the hidden allergens. Hence, a novel method was developed for authentication by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Almond, peanut, walnut and soybean were hydrolyzed, followed by separation by NanoLC-Triple TOF MS. The obtained fingerprints were identified by ProteinPilotTM combined with Uniprot, and 16 signature peptides were selected. Afterwards, plant protein beverages treated by trypsin hydrolysis were analyzed with UPLC-MS/MS. This method showed a good linear relationship with R2 > 0.994 03. The limit of quantification (LOQ) were 0.015, 0.01, 0.5 and 0.05 g/L for almond, peanut, walnut and soybean, respectively. Mean recoveries ranged from 84.77% to 110.44% with RSDs < 15%. The developed method was successfully applied to the adulteration detection of 31 plant protein beverages to reveal adulteration and false labeling. Conclusively, this method could provide technical support for authentication of plant protein beverages to protect the rights and health of consumers.