Abstract: Ultrafiltration membranes casted from hydroxy alkyl cellulose acetate polymers and their transport properties were studied. The rejection of the membranes is greater than 92% (0.05% BSA solution;and water flax greater than 25mL/cm²h under the 0.2 MPa operating pressure. The dependence of membranes performance among the polymer concentration, the evaporative time, the kind of coagulating agent and the temperature of coagulating bath were discussed, when the organic compounds containing different functional groups were used as the second additives. The results showed that if these organic compounds with formative ability of hydrogen bond to polymer were selected, the membrane performances were improved, becaus; of the increase of solution ability of polymer in solvents.