Quercetin nanoparticles encapsulated by Polysorbate 80 were produced by supercritical fluid extraction of emulsion. To analyze the effect of supercritical fluid parameters on organic solvent extraction by scCO(2), Peng-Robinson equation of state was employed to obtain the pressure-composition diagram of the mixture system concerned. Also, Huang equation was adopted in combination with Peng-Robinson equation to calculate the density of the solvent/CO2 binary system. The effects of supercritical fluid parameters such as pressure and temperature on emulsion stability in the emulsion extraction stage and extraction efficiency in both emulsion and solution extraction stages were examined experimentally. The analytical and experimental results showed that phase separation could happen in the emulsion extraction stage because of the swelling and the rapid decrease in the density of ethyl acetate droplets in the emulsion to the minimum density point as the mole fraction of CO2 in ethyl acetate increased with the rise in pressure below the mixture critical point. To avoid the minimum density point, a lower pressure (<6 MPa) could be employed to guarantee the emulsion stability while the similar level of extraction efficiency in the emulsion extraction stage was retained. The supercritical fluid extraction was proven to be very efficient in reducing the content of residual organic solvent in the solution extraction stage with the minimum residual content as low as 5.3 ppm. (C) 2019 Published by Elsevier Ltd.