Fore many years, polymeric materials have been modified by using fillers to produce composite materials with improved characteristics and wider application than the unfilled polymers. Inorganic fillers such as mica, fiberglass, talc, clay, etc. have been widely used. At recently, inorganic fillers have been incentives to their substitution by wood-based fillers because of advantage of low density relative to inorganic filler systems. Also due to characteristics such as low cost, high availability, good physico-mechanical properties and biodegradability, these material could be particularly useful in the formation of composite materials. In this study, to obtain optimum condition of the mechanical properties we were examined for various phenolic resin/wood powder ratio and evaluated the properties of their composites. When the content of phenolic resin is 45 wt%, these composites showed maximum the mechnical strength. In order to improved mechanical properties, modification agents used polyurethane and appeared the maximum value at the 5 phr.