In this study, essential oils were extracted from peels of orange (Citrus sinensis) by employing hydrodistillation. The materials were collected in Ben Tre Province, Vietnam and the process was optimized by varying some experimental parameters including temperature, water-to-material ratio, extraction time and material size. The obtained essential oil was analyzed by Gas Chromatography-Mass Spectrometry to determine chemical composition. The maximal essential oil yield was determined as approximately 4%, obtained at the following conditions: ratio of water and lemon peels of 3:1 (mL/g), 60 mins and130°C. GC-MS results revealed that Limonene (98.454%), β-Myrcene (0.997%), and α-Pinene (0.549%) are the major constituents in the essential oil.