The composition and the bioactivity of the essential oil of Artemisia anomala, a traditional medicinal herb in China, were investigated. The composition of the essential oil was analyzed by gas chromatographyâmass spectometry (GCâMS), and a total of 39 components representing 98.1% in this plant were identified. The main constituents were camphor (18.3%), 1, 8-cineole (17.3%), Î²-caryophyllene oxide (12.7%), and borneol (9.5%). The antimicrobial activities of the oil were separately evaluated against six micro-organisms, Bacillus cereus (CMCCB 63301), Micrococcus flavus (ATCC 14698), Escherichia coli (ATCC 11775), Pseudomonas aeruginosa (ATCC 10145), Staphylococcus epidermidis (ATCC 12228), and a clinical-isolated strain Staphylococcus aureus. The results showed that the oil possessed inhibitory activity against B. cereus, M. flavus, E. coli, S. epidermidis, and S. aureus, among which the best inhibition was observed against B. cereus with a MIC of 0.313 Î¼L/mL. The antiproliferative activities of the oil were assessed against four human tumor cell lines, A459 (human lung adenocarcinoma), BRO (human melanoma), MCF7 (human breast cancer), and PC3 (human prostate). The oil showed the ability to inhibit proliferation of human cancer cells. And the MCF7 cell line was the most sensitive to the oil with an IC50 of 0.09.