The volatile constituents of leaves/tom Eucalyptus dunnii, including oil fraction and water-soluble fraction, were extracted and determined. Oil fraction of volatile components was obtained through steam distillation. Ether was used as a solvent to extract the water-soluble fraction of the volatile compounds from the left liquid after steam distillation in order to know the quantity and constituents of volatile compounds dissolved in the water phase. To the oil fraction,yield of oil was 3. 670//00 (dry weight basis), and to the water-soluble fraction,it was 0.85% (dry weight basis). Both oil fraction and water-soluble fraction were analyzed by gas chromatography-mass spectrometry method. The results showed that 52 compounds that were 97.04% of the oil fraction were identified and 36 compounds that were 83.52% of the water-soluble fraction were identified. The major constituents in oil fraction were 1,8-cineole (24.71%), followed by aromadendrene (9. 10%), γ-terpinene (8.87%), α-pinene (7.67%). Aromadendrene (19.40%) and globulol (15. 670//00) were found to be the major compounds in the water-soluble fraction.