Spearmint oil known as aromatic volatile compound of plants are widely used in food industries. In the present study, supercritical carbon dioxide (SC-CO2) extraction is used to extract the essential oil from spearmint leaves. In this way, a series of extraction experiments are designed to investigate the effect of different operating conditions such as extraction pressure (85-120 bar), extraction temperature (38-50 degrees C), CO2 flow rate (0.059-0.354g/min), mean particle size (0.177-2mm) and dynamic extraction time (20-120min) on efficiency of the extracted essential oils. In the last step, not only a second order polynomial equation is developed to obtain the optimal SC-CO2 extraction parameters, but also the composition of extracted essential oil at optimum operating condition is analyzed using gas chromatography-mass spectrometry (GC-MS). (C) 2017 Elsevier B.V. All rights reserved.