The removal efficiencies of strontium, cesium and cobalt by inorganic membrane with cut-off 8kD were studied. In order to improve the removal efficiency of non-active nuclides, soluble macropolymers sodium poly(acrylic) acid (NaPAA) of different molecule sizes were selected as chemical assistant reagents to make comparative experimental studies. The molecule of 8000,50000 and 100000 D NaPAA were used. The flux and removal rates of different systems were mainly studied. The results show that for inorganic membrane with pore size of 8kD molecule of 50000 Da NaPAA is the best selection for assistant reagents.