Using dimethyl sulfoxide (DMSO) as a solvent, the polyacrylonitrile/soy protein isolate/polyurethane (PAN/SPI/PU) blend solutions and wet spun fibers were prepared. The rheological properties of the PAN/SPI/PU solution were investigated. Investigations of the structure and properties of the PAN/SPI/PU fibers involved Fourier transform infrared, enzymatic hydrolysis, scanning electron microscopy, mechanical properties, dye adsorption, contact angle, and moisture regain nneasurements. The results showed that all PAN/SPUPU Solutions possess pseudoplastic properties, and there are opposite effects of Sill and PU in the PAN/DMSO Solution. The apparent viscosity, the amount of non-Newtonian fluid and the extent of structuralization of the PAN/DMSO solution increase with the addition of SPI, whereas these features all decrease with the addition of PU. The biodegrability, the absorption of acidic dye and the moisture regain increase with the proportional increase in weight of SPI in the fiber blend.