Two types of polypropylene(PP) and Korean pine sawdust wood flour were used as matrix and filler materials for wood/plastic composites. These composites were prepared by melt-blending process in a single screw extruder. Maleic anhydride modified polypropylene(MAPP) was used as coupling agent. The WF(wood flour) was added up to maximum 50 wt% and the coupling agent was added up to 15 wt%. Without the coupling agent, the tensile modulus was improved with increasing amount of WF, but the tensile strength and the impact strength were decreased. The tensile strength could be improved by adding the coupling agent, but the impact strength was not affected. The reduced properties were caused by some defects formed from decomposition of the WF at the high processing temperature. For solving this problem, the processing conditions such as temperature setting, compounding route and pretreatment of WF were checked with two kinds of polyproplene which have different level of melt index. To evaluate the properties, tensile, impact and flexural properties were measured and the fracture surfaces of the composites were investigated by SEM. Also, the effect of water absorption on the properties was evaluated.