Soy protein isolate(SPI) based edible film as matrix materials have been prepared using the casting techniques. Ultrasound treatment (UT) could represent an interesting strategy for improving Soy protein film appearance. Different UT exposure times were applied to film-forming dispersion. The aim of this work was to investigate the effect of ultrasound treatment on Soy protein films at molecular structure and mechanical properties. The results showed that the structure of SPI film became more homogeneous and the properties has been improved largely after treated by ultrasonic, with the output power 1000 w for 16 s the tensile strength was the best; for 12 s, elongation reach the peak.