The antifungal activities of essential oil from four spices, Anethum graveolens L. (Dill), Foeniculum vulgare Mill. (Fennel), Coriandrum sativum (Coriander), Zanthoxylum spp. (Prikhom), against fungus isolated from bird chili powder (Aspergillus flavus) were investigated. The preliminary study on antifungal activity was evaluated at a concentration of 1µl/ml by poisoned food technique in solid culture. A. graveolens L. oil exhibited highly effective antifungal activity, thus A. graveolens L. was selected to determine the minimal inhibitory concentration (MIC) using the concentrations of the essential oil between 0.25 and 2µl/ml. The wet and dry mycelial weights of the treated fungus were also determined in a liquid culture. The minimum inhibitory concentration of A. graveolens L. for the tested fungus was found to be 2.0µl/ml on 9th day of the mycelial growth inhibition. Thus, the essential oil of A. graveolens L. could be potentially used as an alternative food preservative against spoilage caused by the fungus.