A series of casting films of starch and tannin-based polyurethane were prepared and the effect of tannin and starch amounts on the properties of polyurethane was investigated．It was found that when tannin was added

the thermal behavior and mechanical properties of films were improved

especially when the content of tannin reached 60％ (weight percent in biomass)

tannin and the network of starch-based polyurethane interpenetrated and showed good miscibility．Its integral procedural decomposition temperature (IPDT) was 375℃

its tensile strength and Young’s modulus were 51.9 MPa and 308.4 MPa

respectively．The results indicated that tannin had great effect on the density of crosslinking

miscibility of components and the morphology of starch polyurethane．The degradation test in phosphate buffer solutions showed that tannin could adjust the speed of starch polyurethane degradation

to some extent．