Currently, there are an estimated 160-200 species of plants that can produce essential oils. Unfortunately, research on the composition and use of these oils is still limited. This study aims to investigate the characteristics of essential oil derived from root bark of Sintok wood (Cinnamomum sintoc Blume), its antifungal activity against the fungus Pleurotus ostreatus, and its chemical components. A kilogram of Sintok root bark collected from Hampangen Educational Forest of the University of Palangka raya was distilled within the boiled system to get its essential oil before used to test its fungal activity against P. osterams. Data of inhibition fungus growth were analyzed for IC50 determination. The Sintok root bark essential oil was further analyzed by GC-MS to determine its chemical compound. The results show, first, the yield of essential oils from Sintok root bark is 0.16"/o, the acid number was 2.24, and the ester number was 19.63. Anti-fungal activity test of Sintok essential oils against P. ostreatus shows that the fungus remained alive at oil concentration of 530 mu g/mL, and the fungus died when oil concentration beteween 65-1.000 mu g/mL. Sintok root bark essential oil has optimum anti-fungal properties at a concentration of 48.69 mu g/mL. Second, there are 15 chemical compounds contained in Sintok root bark essential oils, with three main compounds namely methyl eugenol (77.14%), methyl cinnamate (17.43%) and 4-Nonylphenol (1.35%).