In this study, a sensitive and selective method for simultaneously quantifying eight major components (four iridoid glycosides, three phenethylalcohol glycosides and one furfural derivative) of Rehmanniae Radix by high performance liquid chromatography coupled with triple-quadrupole mass spectrometry (HPLC-TQ-MS) was developed. The sample preparation was executed using an optimised ultrasonic method with complete extraction efficiencies of eight analytes. For mass spectrometry, selected ion recording (SIR) scan mode was used to improve the sensitivity and selectivity. The established method was validated in terms of linearity, sensitivity, precision, accuracy and stability, and successfully applied to determine the contents of the eight analytes in different batches of raw and processed Rehmanniae Radix, which confirmed that the established method was reliable and useful for "holistic" quality evaluation of Rehmanniae Radix. The quantitative results indicated that the quality of commercial raw or processed Rehmanniae Radix was remarkably inconsistent.