Abstract: In order to improve the interfacial bonding strength of wheat straw fibers and polypropylene (PP), the wheat straw fibers were treated by combined treatment. The surfaces of fibers were pretreated by 5 methods, such as NaOH, acetic acid, hot water, steam explosion and microwave, and then compounded by coupling agent treatment. The wheat straw/PP wood-plastic composites were prepared by blending with PP and wheat straw through melt blending and molding. The mechanical properties, water absorption and moisture absorption performance of the PP wood-plastic composites filled with different surface treated wheat straw fibers were investigated. The tensile sections of the composites were observed by the stereo microscope. The results showed that the mechanical properties, water absorption and moisture absorption performance of PP composites filled with combined treated fibers were excellent that the composites filled with coupling agent treated fibers. It was found that the composites with wheat straw treated by NaOH and acetic acid had good mechanical properties and anti-water absorption and anti-moisture absorption performance, followed by the composites with wheat straw fibers treated by hydrothermal and steam explosion. After combined treatment, the surface of wheat straw became rough, so that the interfacial adhesion of straw fibers and PP matrix was improved. The results of this paper had great practical significance on improving the properties of wheat straw/waste PP wood-plastic composite by straw fiber surface treatment.