A temperature-responsive composite membrane with tunable responsive behavior was prepared by covalently grafting a polymeric ionic liquid (PIL) functionalized temperature-responsive copolymer onto the brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) supporting membrane. The “switch” effect of the composite membrane can be facilely adjusted by tuning the counter-ion of PIL units of the grafted copolymer based on the transformation between hydrophilicity and hydrophobicity of PIL. The response temperature of the composite membrane was decreased with increasing the content of hydrophobic PIL units. Both the pure water flux and rejection of dyes and polyethylene glycol (PEG) of the composite membrane show a good responsiveness with changing the temperature. The study provides an easily available, flexible and effective method for the design and preparation of a temperature-responsive membrane with tunable responsive behavior to satisfy various applications.