A new material was prepared by formation of polystyrene in situ wood porous structure from styrene monomer through thermal-catalyst treatment. And the performance of such wood-polymer composite, containing mechanical properties and durability, was also tested. The SEM results showed that polymer was generated inside wood, and filled in wood cellular structure. The mechanical properties of such wood-polystyrene composite including modulus of rupture (MOR), modulus of elasticity (MOE), compression strength and hardness, were respectively improved 38%, 77%, 21% and 97% over untreated wood. And the durability of the novel composite involving dimensional stability, decay resistance and stability against weather erosion were remarkably improved than those of untreated wood. Such composite can be widely used in fields of construction, traffic and interior decoration, which greatly enhanced the utilization of low-valued wood material instead of high-quality wood.