Basil (Ocimum basilicum L.) essential oil is potential to be used as an antimicrobial agent. The purpose of this study were to determine the chemical constituents of the essential oil of basil and determine its potency as food preservative. Analysis of chemical compound was performed with Gas Cromatography Mass Spectrometer (GCMS). Potency as food preservative was analyzed with turbidimetry method, organoleptic test and descriptive observations on the bacterial growth on Nutrient Agar (NA) media. Components of basil essential oil from Kedungbanteng, Purwokerto were mainly consisted of E-citral (22,79%), Z-citral (15,60%), α-humulene (12,56%), and β-caryophyllene (11,74%). Components of basil essential oil from Ajibarang were mainly consisted of E-citral (30,91%), Z-citral (25,94%), and caryophyllene oxide (6,49%). Basil essential oil was potential to be used as tofu and chicken preservative. It’s obtained from Kedungbanteng, Purwokerto at concentration of 125 μg / ml was capable of preserving tofu for 4 days and prolonging the shelf life of tofu for 2 days. Basil essential oil obtained from Ajibarang at concentration of 625 μg / ml was capable of preserving chicken for 15 days and prolonging the shelf life of chicken for 6 days.