Abstract: Poly(lactic acid) (PLA)/corn straw powder composites was prepared by a solution casting method using PLA and corn straw powder as raw materials. Effects of raw material ratio and coupling agent type and content on chemical structure, interfacial compatibility, thermal stability and mechanical properties of the composites were investigated. The results indicated that mechanical properties of the composites increased at first and then tended to decrease with an increase of the content of corn straw powders. The composites achieved the maximum mechanical properties at the corn straw content of 20 wt %. The addition of silane (KH550) or titanate coupling agent could improve the compatibility between the corn straw powders and PLA and enhance the bonding between two materials, thus improving the thermal stability and mechanical properties of the composites but reducing their water absorption. The composites gained the optimum properties with the addition of 1.5 wt % of KH550 or 3 wt % of titanate coupling agent.