In the present study,the effect of three critical SFE variables namely solvent flow rate (1-7 g/min),pressure (20-50 MPa) and temperature (30-60 ℃) on extraction yield of Nigella sativa oil was investigated by using response surface methodology (RSM).Thus,twenty operating treatments were established based on a three-factor central composite design (CCD) involving 8 factorial points,6 axial points and 6 center points.The significant (p < 0.05) polynomial response model with high coefficient of determination (R2 ≥ 0.99) was accurately fitted to the experimental data for describing the changes of extraction efficiency as function of SFE operating variables.