Two kinds of blend membranes of regenerated cellulose and silk fibroin (SF) were prepared by coagulating the mixture solution of cellulose and silk fibroin in cuoxam with acetone-acetic acid (4:1 by volume) and 10 wt.% NaOH aqueous solution, respectively. The compositions, miscibility, structure, water permeability of the blend membranes were measured, and the effects of various coagulants and the weight percent of SF (w(SF)) on the structure and microporous formation of the blend membranes were investigated and discussed. FT-IR, SEM and dynamic mechanical thermal analysis (DMTA) indicated that cellulose/SF blend, obtained by coagulating with acetone-acetic acid, was miscible in the blend membranes, and a strong hydrogen bond interaction exists between cellulose and SE The crystallinities of the blend membranes obtained thereby decreased. Cellulose/SF blends, prepared by coagulation used 10% NaOH aqueous solution, formed microporous membranes having larger pore size (2r(f)=102 nm) and water permeability UFR (169 ml m(-2) h(-1) mmHg(-1)) with an increase of w(SF). In this case, the hydrogen bonds between cellulose and SF were broken, allowing the SF to be removed by extraction, leaving a microporous surface modified cellulose membrane.