Abstract: The straw-powder/PP composites were made by compression molding process. Mechanical properties of the composites were tested, such as tensile and flexural properties by universal material testing machine and impact property by impacting testing machine. The microstructure of cross section was observed by stereomicroscope. The result showed that straw-powder/PP composites with relatively good mechanical properties could be obtained if the straw-powder could be modified by silane coupling agent KH570. Mechanical properties of the composites will be better when the content of the straw-powder with 60 mesh is exactly 50% of gross weight. The microstructure surface of composites with 60 mesh straw-powder can be smooth.