Nowadays, increasing consumption of fossil fuels and limite of reserves in certain parts of the world, as well as environmental pollution due to the use of fossil fuels, has drawn the attention of researchers to alternative fuels with plant sources. Salicornia is one of the plant sources for biodiesel production, Which has a rich oil content. supercritical extraction method using supercritical carbon dioxide fluid was used to extract oil from Salicornia plant. In this research, the response surface design method and the central composite design were used to design of experiments in the separation process under different operating conditions. Also, the effect of four variables of temperature, pressure, supercritical carbon dioxide flow rate and dynamic time in the range of 35 to 75 ° C, 12 to 32 MPa, 0.8 to 2.2 ml / min, 40 to 160 minutes on the efficiency and recovery rate of oil extraction has been investigated. Laboratory results in oil extraction achieved a good fit with a relativity coefficient of 96.60 and a modified relativity coefficient of 93.62. The results of laboratory data and modeling showed that with increasing pressure, the percentage of oil recovery increases. This observation and prediction is due to increasing in the density of supercritical fluid at high pressures, which leads to an increase in the solubility of supercritical carbon dioxide.With increasing the temperature to the range of 55 to 65 °C the oil recovery percentage increase due to the increasing in vapor pressure of the soluble components, which increases the solubility of the solute in supercritical carbon dioxide. However, with further increasing of temperature from the mentioned range, the decrease of oil recovery percentage shows that this decrease is due to the decreasing of solvent density and further decrease of supercritical carbon dioxide solubility. In addition, increasing the dynamic time has increased the oil recovery percentage, which can be attributed to the effect of the driving force between the fluid and the sample to transfer the mass due to the passage of fresh solvent. However, it was observed that at higher times the slope of the graph is decreasing and it was predicted that this is due to the reduction of oil in the sample and consequently the reduction of oil recovery percentage. In addition, it was predicted that increasing the flow rate to about 1.9 ml / min due to reducing the thickness of the mass transfer layer around the solid particles and consequently reducing the mass transfer resistance has increased the oil recovery percentage, However, with further increase of flow rate due to reduced residence time and weak contact of solvent with solid, the percentage of oil recovery decreases. The response surface design method achieved optimal operating conditions for oil extraction at 66.51 °C, pressure 32 MPa, flow rate of 1.9 ml / min and dynamic time of 160 minutes and the optimum efficiency of 70.2 Percent calculated that with laboratory results obtained this value 68.57, a good approximation was obtained. Finally, the amount of biodiesel obtained from the oil reaction obtained from the optimal extraction state was 92%. Keywords: Supercritical Fluid, Biodiesel, Salicornia, Response Surface Method, Extraction.