Soy protein isolate is an abundant, inexpensive, and renewable industrial raw material that provides an environmentally-conscious alternative to fossil fuel source. In this study, novel, biodegradable films were prepared from soy protein isolate (SPI), glycerol, polyacrylamide (PAM), and 1,2,3-propanetriol-diglycidyl-ether (PTGE). The mechanical, hydrophilic, biodegradation, and compatibility properties of the SPI/PAM/PTGE films were then thoroughly examined. The effects of the incorporation of PTGE and PAM on the properties of the films were investigated using Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetry. Tests were also performed to determine total soluble matter, mechanical properties, and water barrier. Results showed that the mechanical properties and water resistance of the modified SPI films improved considerably after the incorporation of PAM and PTGE. Compared to traditional commercial polyethylene films, the PTGE/PAM-modified SPI films showed higher biodegradability, suggesting a convenient and efficient method of preparing environmentally-friendly film material.