The chemical composition of the essential oil of Mentha spicata from China was investigated by the Gas chromatography/mass spectrometry (GC/MS) analysis. 21 compounds were identified, representing 97.10% of the total oil. The major compounds in the essential oil were carvone (65.33%), limonene (18.19%), dihydrocarvone (2.97%) and camphene (2.34%). The oil showed antioxidant activity assessed using DPPH assay. The antimicrobial activity was investigated in order to evaluate its efficacy against 5 microorganisms using MIC and MBC methods. The results indicated that spearmint oil showed inhibitory and bactericidal effect on all test microorganisms. It was highly effective against E. coli, S. cerivisiae and P. citrinum. S. cerivisiae was more susceptible to spearmint oil (MIC 0.78125 uL/mL and MBC 6.25 uL/mL). The cytotoxicity of spearmint oil was evaluated on Hela cells using the MTT assay. The oil showed quite strong cytotoxicity on the cell lines with an IC₅₀of about 2.08ug/mL.