Abstract: The optimal extraction process of unsaturated fatty acids from Eucalyptus leaves was obtained by orthogonal test based on factors such as different solvents,material particle size,solid-liquid ratio,immersion time and extraction time. The components of extracts were analysed by GC-MS after methylation. The results from 16 tests of 5 factors and 4 levels showed that the extraction yield was 14.9 % on the optimal extraction conditions, i.e., acetone as solvent, material particle size 0.075-0.150 mm, solid-liquid ratio 1:15(g:mL), immersion time 8 h and extraction time 1.5 h. Six compounds including five fatty acids, for example unsaturated fatty acids, linoleic acid and linolenic acid, were indentified. There was 36.01 mg unsaturated fatty acids in 10 g dried Eucalyptus leaves. Eucalyptus leaves have potential values to develop because of unsaturated fatty acids.

Key words: Eucalyptus leaves, unsaturated fatty acid, orthogonal test, extraction, composition analysis