In membrane separation technology, designing and preparing membranes with excellent hydrophilicity and separation performance remains a great challenge. In this study, a thermo-responsive copolymer (DexPNI) is made by RAFT polymerization and used as an additive for polyethersulfone membrane modification to improve the hydrophilicity of the membrane also impart thermal response behavior. The water contact angle of the modified membrane is significantly decreased from 89.3 degrees to 58.8 degrees compared to pristine polyethersulfone membrane. The pure water flux of the modified membrane is found to be 118.5 L m(-2) h(-1), and has a high rejection for BSA above 95%. The obtained results show that the modified membrane has excellent hydrophilicity and rejection properties. Moreover, the pore size of the modified membrane can be adjusted for molecular separation by simply controlling the extension and contraction of the thermally responsive polymer chains.