PURPOSE: To obtain a reverse osmosis membrane having chlorine resistance, high salt expulsion property and extremely high fluxes by interfacially polymerizing a para-arom. aliphat. diamide or diimide salt expulsion layer on a microporous polymer support.

CONSTITUTION: The mixture composed of trimesoyl chloride contg. ≥20wt.% trimesoyl chloride and isophthaloyl chloride and the arom. aliphat. amine/imine of formula I (where Ph=para-substd. phenylene group, R1=1-2C alkylene group, R2=H or 1-2C alkyl group) are interfactially polymerized on the flat microporous polymer support of polysulfone, etc. The thus resulted composite reverse osmosis membrane has the good chlorine resistance, the high salt expulsion property and the extremely high fluxes.