Three different poly(thioether amide)s containing trifluoromethyl (FT), sulfonyl (ST) or pyridinediyl group (PB) were prepared by a Michael-type polyaddition reaction. The separation performance of their membranes was studied and compared with each other on the structure difference. Their tight membranes were commonly water-permselective in pervaporation (PV) of a water-ethanol mixture. The order of separation factor was ST > PB > FT, with ST especially being highly water-permselective. The evaporation time greatly influenced PV performance, and FT readily formed an opaque membrane on gelling after a short evaporation period, showing an ethanol-permselective behavior.