Blend films from nature soy protein isolates (SPI) and synthetical poly(vinyl alcohol) (PVA) compatibilized by glycerol were Successfully fabricated by a Solution-casting method in this Study. Properties of compatibility, mechanical properties, and thermal stability of SPI/PVA films were investigated based on the effect of the PVA concentration. XRD tests confirm that the SPI/PVA films were partially crystalline materials with peaks of 20 = 20 degrees. And, the addition of glycerol will insert the crystalline structure and destroy the blend microstructure of SPI/PVA. [Differential scanning calorimetry (DSC) tests show that SPI/PVA blend polymers have a single glass transition temperature (T-g between 80 and 115.0 degrees C, which indicate that SPI and PVA have good compatibility. The tension tests show that SPI/PVA films exhibit both higher tensile strength (sigma(b),) and percentage elongation at break point (P.E.B.). Thermogravimetric analysis (TGA) and water solubility tests show that SPI/PVA blend polymer has more stable stability than pure SPI. All the results reflect that SPI/PVA/glycerol blend film provides a convenient and promising way to prepare soy protein plastics for practical application. (c) 2008 Wiley Periodicals, Inc. J AppI Polym Sci 110: 3706-3716, 2008