Abstract: In this article, a type of biodegradable PLA/wheat straw composites were prepared by a compression-molding method using metallocene polyethylene (mPE) and POE as impact modifiers. The effects of type and loading of impact modifiers on the mechanical properties and water absorption of the composites were investigated and their crystalline and chemical structures were analyzed by XRD and FTIR spectroscopy. The results indicated that the Rockwell hardness and tensile, bending and impact strength of the composites presented an increasing trend first and then tended to decrease with an increase of mPE/POE content, When the content of impact modifierswas in the range of 5 wt%~10 wt%, the composites achieved optimumproperties.