Abstract: Gas chromatography/mass spectrometry, chemometric resolution method (CRM) and overall volume integration method were used to analyze the essential components of herbal pair Herba Ephedrae-Ramulus Cinnamomi (HP HE-RC) and compare it with that of single herbs HE and RC. 72, 68, and 97 essential components in essential oil of HE, RC, and HP HE-RC were determined, accounting for 90.08%, 91.62%, and 89.76% of total contents of essential oil of HE, RC, and HP HE-RC, respectively. The numbers of essential components of HP HE-RC are almost the summation of that of two single herbs, but some relative contents of them are changed. Some new components, such as 1,6-dimethylhepta-1,3,5-triene, tetracyclo［4.2.1.1(2,5).0(9,10)］deca-3,7-diene, globulol, (E,E)-6,10,14-trimethyl-5,9,13-pentadecatrien-2-one, etc. have been found in HP HE-RC because of chemical reactions and physical changes during the course of decocation.