Schiffs bases of polyallylamine were synthesized by the reaction with four aldehydes. Salicylaldehyde (S)- and 2-pyridinecarboxaldehyde (P)-Schiff's base could be used as reverse osmosis membranes when crosslinked with divinyl sulfone, diacetyl or ethylene glycol diglycidyl ether. S-base membrane had a high mechanical strength but poor water permeability (K1), while P-base membrane showed a high rejection, particularly against CoCl2, and a high K1 because of chlate formation, but poor strength. The membranes of P-base and a hybrid PS-base exhibited a possibility of separating alkali metal salts and transition metal salts from each other.