The reverse osmosis (RO) separation of aqueous organic solutions, such as alcohols, amines, aldehydes, acids,ketones, and esters etc., by PAA (polyacrylic acid)/PSF (polysulfone) composite membrane has been studied. It was foundthat the separation results for aliphatic alcohols, amines and aldehydes are satisfactory, the solute rejection (R_a) and thevolume fluxes of solutions (J_v) for 1000 ppm ethanol, ethylamine and ethyl aldehyde are 66.2%, 61.0%, 84.0% and 0.90×10~(-6), 0.35×10~(-6), 0.40×10~(-6) m~3/m~2·s, respectively, at 5.0 MPa and 30℃. R_a increased with increasing molecular weights ofalcohols, amines and aldehydes, and the R_a for n-amyl alcohol, n-butylamine and n-butyl aldehyde reached 94.3%, 88.6%and 96.0%, respectively. Satisfactory separation results (R_a>70%) for ketones, esters, phenols and polyols have beenobtained with the PAA/PSF composite membrane. The effect of operating pressure on the properties of reverse osmosis hasalso been investigated. Analysis of experimental data with Spiegler-Kedem’s transport model has been carried out and themembrane constants such as reflection coefficient σ, solute and hydraulic permeabilities ω and L_p for several organic soluteshave been obtained. The reverse osmosis (RO) separation of aqueous organic solutions, such as alcohols, amines, aldehydes, acids, ketones, and esters etc., by PAA (polyacrylic acid) / PSF (polysulfone) composite membrane has been studied. It was foundthat the separation results for aliphatic alcohols, amines and aldehydes are satisfactory, the solute rejection (R_a) and the volume fluxes of solutions (J_v) for 1000 ppm ethanol, ethylamine and ethyl aldehyde are 66.2%, 61.0%, 84.0% and 0.90 × 10 ~ -6, 0.35 × 10 -6, 0.40 × 10 -6 m 3 / m 2 · s, respectively, at 5.0 MPa and 30 ° C. R a increased with increasing molecular weights of alcohols, amines and aldehydes, and the R_a for n-amyl alcohol, n-butylamine and n-butyl aldehyde reached 94.3%, 88.6% and 96.0%, respectively. Satisfactory separation results (R_a> 70%) for ketones, esters, and polyols have beenobtained with the PAA / PSF composite membrane. The effect of operating pressure on the properties of reverse osmosis has been investigated. Analysis of ex perimental data with Spiegler-Kedem’s transport model has been carried out and themembrane constants such as reflection coefficient σ, solute and hydraulic permeabilities ω and L_p for several organic solutes have been obtained.