A novel Wood-Polymer Composite, Wood-PSt composite combining both advantages of wood and polystyrene was fabricated by determining the polymerization craft of monomer in wood porous structure through impregnating monomer into wood pores and followed by in-situ polymerization through a thermal-catalyst treatment. The performance was examined, and its structure was also characterized by SEM and FTIR. The results indicate that the optimum polymerizing craft is: 80oC, 8h and 3% AIBN. Under the optimum craft, the mechanical properties involving modulus of elasticity and compression strength were linearly increased with content of polystyrene. SEM and FTIR show that styrene polymerized under the employed polymerization craft, and the resultant polystyrene relatively full generated in wood cellular structure, in accordance with the results of the optimum polymerizing craft. Such composite having good mechanical properties and biomass features can be widely used in fields of construction, traffic and furniture.