Abstract: The chemical composition-antibacterial activity relationship model of lavender essential oil was established to recognize the active compounds base on gas chromatography-mass spectrometry (GC/MS). Seventeen volatile oil samples collected in Xinjiang which belong to three different lavender species (C-197(2), French blue, H-701) were analyzed by GC/MS. In the three varieties of lavender, 39 characteristic peaks are identified by mass spectral data and retention indices from the literature. Functional properties of the essential oils were checked by determining antibacterial activity against Staphylococcus aureus and the IC₅₀ value was determined. Principal component analysis (PCA) identified three main chemical clusters among lavender essential oils. PCA analysis shows that the essential oils belong to the linalool and lavandulol cluster, which are the most antimicrobial activity. The chemical composition-antibacterial activity relationship of lavender essential oil was investigated by partial least squares analyses (PLS). The results show that linalool, lavandulol, caryophyllene oxide, α-terpineol, cryptone, cis-ocimene, nerolidol, linalool oxide and τ-cadinol are significantly related to antibacterial activity according to PLS analyses.