The effects of wood flour content (6080%) and m-TMI-g-PP content (014%) on the properties of wood flour/polypropylene composites (WF/PP) were investigated by means of mechanical properties, thermal analysis, dynamic rheological analysis, and scanning electron microscopy (SEM). The results demonstrated that WF significantly increased the mechanical properties, char yield, heat deflection temperature (HDT), vicat softening temperature (VST), T-c, G, G, and . However, WF above 70% led to decreased mechanical properties, so for the comprehensive consideration of the cost and environmental issues, 70% WF is the best. With the addition of m-TMI-g-PP, the mechanical properties, thermal stability, HDT, VST, oH(m), and T-m of composites were all got improvement, which was attributed to the strong interfacial interaction of m-TMI-g-PP on composites. However, when it exceeded 10%, the mechanical properties of the composites declined, it probably formed a separate phase in the PP matrix. Therefore, the 10% m-TMI-g-PP was chosen in WF/PP. In addition, the results were all further confirmed by SEM analysis.