Deng's herbal tea (DHT), a famous traditional Chinese herbal tea consisting of six traditional Chinese medicines (Honeysuckle, Chrysanthemum, Rhizoma imperatae, Folium mori, dandelion and liquorice), is widely used in China for its health benefits. In this paper, a rapid resolution liquid chromatography coupled with mass spectrometry (RRLC–MS) method was developed for the identification and determination of the major constituents in DHT granules. A good RRLC separation was achieved using an Agilent Poroshell 120 SB-C18 column and gradient elution (0.5% formic acid in water/acetonitrile) within 30 min. Twenty-eight compounds were identified or tentatively characterized based on their exact molecular weights and fragmentation patterns. Fifteen major bioactive constituents of those 28 compounds were chosen as the benchmark substances. Their quantitative analyses were performed by a triple quadrupole tandem mass spectrometer (MS/MS) operating in multiple-reaction monitoring mode, and a full quantitative analysis of the 15 major constituents was performed by our developed RRLC–MS/MS method in only 10 min. Of the 16 DHT granule samples tested, the quality of the results was stable, which confirms that the developed method was efficient and robust for the quality control of DHT granules.