So many articles on fennel (Foeniculum Valgare Mill.) essential oil constituents have been published. The goal of this article is influnce of preparations of essential oil on quality and quantity of the essence. We prepared the essences by two methods (hydrodistillation and steam distillation). Hydrodistillation were conducted in four different process time (15, 30, 60 and 150 minutes) and the latter conducted at 150 minutes. The oils were analysed by GC and GC/MS. 37 major compounds were detected in the oild totally 91.37 to 97.57% of the essences were consisted of these compoundes. E Anethole, Estragole and D-(+)- Fenchone were the most frequent compounds. The highest percent of anethole was at 30 minute.