The goal of this research was to develop a simple, rapid and sensitive method for simultaneous quantitative determination of salidroside, gardenoside, liquiritin, baicalin, wogonoside, wogonin, saikosaponin A and saikosaponin D in Longchai Decoction by ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC–Q-TOF-MS), in order to control the quality of Longchai Decoction and to analyze the changes of chemical components before and after the compatibility of the component herb drugs. The chromatographic separation was performed on the Waters ACQUITY BEH C18 column (2.1 mm×100 mm, 1.8 μm) using the mixture of acetonitrile and 0.1% (v/v) methanoic acid as mobile phase with a gradient elution program at the flow rate of 0.3 mL/min and the column temperature of 30 °C. The eight components of the standards achieved baseline separation. Regression analysis revealed a linear relationship (r2>0.9998) between the contents and the peak areas of the mixed standard substances. The average recovery rates were between 99.72% and 102.13% with RSD values were less than 2.82% (n=5). The obtained results indicated that the content of index components were higher in co-decoction compared to mixed decoction. This method with a good resolution and high precision can be used for the quality control of Longchai Decoction.