Nitrate-selective ion exchange resins have been synthesized by the reaction of chloromethylated polystyrene - divinylbenzene copolymer and corresponding trialkyl amine ［NR₃〓 NEt₃ ［N(CH₂CH₃)₃］(2), NPr₃［N(CH₂CH₂CH₃)₃］(3),NBu₃［N(CH₂CH₂CH₂CH₃)₃］(4), NPe［N(CH₂CH₂CH₂CH₂CH₃)₃］(5) in ethanol. The functional group of ion exchange resin for the effective NO₃ removal was the order of NPr₃＞ NBu₃＞ NEt₃＞ NMe₃＞ NPe₃.