Modeling of supercritical CO 2 extraction of Hippophae rhamnoides L. seed oil was studied at 15 to 30 MPa and 30 to 45°C. Four mean Hippophae rhamnoides L. particle sizes raging from 0.4 to 1.0 mm were tested. CO 2 flow rate ranged between 0.05 and 0.2 m 3 h -1. A new method that can be used for the simulation of SCFE process was presented. The model was based on differential mass balances along the extraction bed. The equilibrium between the solid and the fluid phase appeared to be the controlling step during the extraction fast period. By a series of transforms and derivatives, the explicit expression of the oil yield, q(z,t), was obtained. It can be used for the SCFE process simulation. In this model, only one adjustable parameter was used: the equilibrium constant between the solvent and the free solute phase, K. A fairly good fitting of the experimental data was obtained by setting K = 10. The Hippophae rhamnoides L. seed oil extraction process was modeled as a desorption process from the seed matter plus a small mass-transfer resistance. ; Department of Applied Biology and Chemical Technology