In this paper, N-Methylmorpholine-N-Oxide (NMMO) was used as solvent for regenerated silk fibroin (RSF). Concentrated solutions with RSF content from 10 to 25 wt% were obtained by dissolving RSF film into NMMO monohydrate. The spinning and rheological properties of RSF/NMMO center dot H2O solutions were studied by a simple piston type single filament spinning apparatus and HAAKE RS150L rheometer, respectively. The results are discussed to understand the influences of shear rate, temperature and RSF concentration on the rheological behaviors of RSF/NMMO center dot H2O and to choose appropriate process condition for spinning. Spinning was performed using a dry-wet spinning process. The regenerated silk fibre was prepared successfully and the tenacity can reach to 3.07cN/dtex. C (c) 2005 Springer Science+ Business Media, Inc.