Shape memory effect (SME) was achieved for cellulosepolyurethane (PU) blends of different compositions in wetdry cycles, featuring that the amorphous cellulose and the PU content served as the fixing phase and the recovery phase, respectively. The dependence on the compositions of the fixity ratio and the recovery ratio was quantitatively measured by tensile tests. The morphological and thermal properties of the blends were further investigated by scanning electron microscopy and thermogravimetric analysis. The storage modulus of the blends varied reversibly in the wetdry cycles, as determined by dynamic mechanical analysis. Furthermore, the microstructure of the blends reversibly changed correspondingly, as determined by wide-angle X-ray scattering diffraction and Fourier transform infrared. It was predicted that the reversible transition in different amorphous cellulose structures triggered by water led to the reversible variation in modulus as well as the wetdry SME of the blends. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012