Objective: To determine the major components of volatile oil from Forsythiae Fructus in different origins by gas phase method, and compare its antibacterial activity in vitro. Method: Volatile oil of 16 batches of Forsythiae Fructus in different origins were extracted by steam distillation method; the major components and content were detected and analyzed by gas chromatog. (GC); their antibacterial activity was analyzed and compared by K-B disk diffusion method. Chromatog. conditions; HP-5 capillary chromatog. column (0.25 mm × 30 m, 0.25 μm). Procedure temperature: initial temperature of 50°C, and increased to 86°C at the rate of 5°C·min-1, kept for 3 min, and then increased to 220°C at the rate of 20°C·min-1, and kept for1 min. Injection port temperature was 230°C, and detector temperature was 250°C. Result: α-Pinene, camphene, β-pinene, myrcene, p-cymene, limonene and α-terpineol had good linear relationship within the range of 0.0165-0.9888, 0.0050-0.3000, 0.0381-2.2860, 0.0032-0.1920, 0.0008-0.0480, 0.0082-0.4920 and 0.0024-0.1440 μg (r≥0.9997) resp. RSDs of the stability test and reproducibility test were less than 3.0%; the recovery of the method was in the range of 99.0%-103.4% (RSD<3.0%). There were differences in the contents of the major components of volatile oil from Forsythiae Fructus in different origins, and the volatile oil had different inhibitory effect against five kinds of the tested strains. Conclusion: The established GC method is simple, accurate and reliable, and can be used for quality evaluation and antibacterial activity evaluation of Forsythiae Fructus.