N-isopropylacrylamide(NIPAAm) was dispersed in polyurethane(PU) solution and crosslinked with N,N’-methylene bisacrylamide(BIS) to form a semi-interpenetrating polymer networks. The synthesized solution was casted into water bathes with and without 0.25M sodium chloride to get a microporous film by wet phase inversion process. The ratios of BIS amount to N-isopropylacrylamide were varied. The structure and properties of polyurethane/ poly(N-isopropylacrylamide) (PU/PNIPAAm) composite film were characterized by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). The swelling behavior of PU/PNIPPAm composite films was evaluated. The results showed that the addition of sodium chloride lower the LCST of PNIPAAm and the PU/PNIPAAm composite films exhibit temperature sensitivity under swollen conditions.