The composite in this case was produced from corn cob flour (CCF), wood ash (WA) and polypropylene (PP). WA with different concentration (1, 3, 5, 10 wt%) served as reinforced filler for corn cob/plastic composite. In order to increase the interfacial adhesion between matrix and filler, the maleic grafted PP was used as compatilizer. The results of infrared spectrum, thermogravimetric analysis, scanning electron microscope, mechanical property and water absorption were reported. The results indicated that the flexural modulus and tensile modulus of CCF/WA/PP composite (CCWPC) increased with increasing the addition of WA. When the addition of WA was 10 wt%, they reached 2550 and 324 MPa, respectively. Furthermore, the flexural strength and tensile strength of CCWPC were lower than those of PP. The moisture absorption of CCWPC increased with adding the loading of WA. The presence of WA also influenced the thermal property of CCWPC.