Abstract: The volatile oil was extracted from fresh leaves and fruits of Callistemon citrinus by hydro-distillation method, with yield of 0.16% and0.48% respectively. 29 components were identified from extracted oil of leaves and 27 ones of fruits by gas chromatography-mass spectrometer(GC-MS), which accounted for 92.84% and 91.71% of their total volatile substance. Among them from leaves, Eucalyptoloccupied 50.67%, α-Pinene19.7%, α-Bornene 7.85%, D-Limonene 3.32% and p-Cymol 2.26%, and that from fruits, α-Pinene 40.91%, Eucalyptol 38.57%, D-Limonene 3.99%and 3-Isopropyltoluene 2.21%. There were only 7 components could be extracted from leaves and fruits, and their relative content was differentbetween leaves and fruits. Experiments were conducted on antimicrobial activities of volatile oil from leaves and fruits with streptomycin sulphate ascontrol against Agrobacterium tumefaciens, Bacillus subtilis, Ralstoniasolanacearum, Xanthomonasvesicatoria and Staphylococcus haemolyticusshowed that volatile oil from leaves was much better than that from the fruit and the control.