We synthesized the zwitterionic homopolymer polysulfobetaine (PBET), which has upper critical solution temperature property, via free radical polymerization in order to examine its suitability as a draw solute for the FO process. The UCST property of the monomer BET were not confirmed, while the UCST of the polymer PBET was observed to be about 41 °C. This result suggests that PBET can be easily recovered from aqueous solutions by cooling them to below the UCST. In an active layer facing feed solution (AL-FS) system containing 20 wt% PBET at a temperature of 50 °C, the water flux and reverse salt flux of PBET were observed to be about 3.22 LMH and 0.36 gMH, respectively. We investigated the suitability of homopolymer having UCST property as draw solute for the FO process for the first time. This study can provide for deep understanding of new method of proceeding draw solute and inspiration for the potential design and synthesis of thermo-responsive organic materials.