Objective To study the essential oil components in herbal pair (HP) of Radix Angelica dahurica-Ligusticum chuanxiong Hort.(RAD-LCH) and its single herb, and to investigate the influence of HP on the components of the volatile oil. Methods Essential oil was extracted from Radix Angelica dahurica and Ligusticum chuanxiong Hort. by steam distillation. Identification of extracted components was accomplished using GC-MS technique combined with library searching and literature comparison. Chromatography analysis was carried out on a TR5-MS capillary column (30 m× 0.25 mm, 0.25 μm); the carrier gas was high-purity helium; the inlet temperature was 250℃; the injection volume was 1 μL, the split ratio 501; constant current mode, the flow rate of carrier gas was 1.00 mL/min; the temperature program was as follows: 50℃ for one minute, rose to 240℃ at 5℃/min and maintained for one minute, then rose to 280℃ at 5℃/min and maintained for one minute. MS condition was as follows: electron impact (EI) ion source, electron energy 70 eV, ion source temperature 200℃, transmission line temperature 280℃, mass scan range m/z:50-650 amu, data acquisition scan mode for full scan, and solvent delay five minutes. Results There were 69, 59, 59, 60 and 78 volatile constituents in RAD, LCH, HP (1:1), HP (4:1) and essential oil of mixture of equal concentration from RAD and LCH (EOEC), and 19 common volatile components were identified. Conclusion Regarding the volatile oil constituents and content, the volatile oil compositions of different HP proportions vary greatly, accompanied by changed contents of volatile oil components of single herb in HP.