The volatile oil was extracted from above-ground part of Melilotus alba Medic. ex Desr. by steam distillation.Chemical constituents and their relative contents were determined by GC-MS and peak area normalization. The results show that 50 chromatographic peaks are detected in volatile oil from above-ground part of M. alba, in which 35 compounds are identified and their relative contents account for 92. 90% of total volatile oil. The compounds with higher relative content are camphor(15. 62%), (-)-4-terpineol(11. 92%), eucalyptol(11. 32%), borneol(10. 31%), 3,3,6-trimethyl-1,4- heptadien-6-ol(4. 51%), 1-(2-furanyl)-1-butanone(3. 71%), terpineol(3. 66%) and pulegone(3. 35%).