Wood as a porous structure has weak durability and unsatisfactory mechanical properties which limits its utilization. For this reason, the study presents a two-step method to prepare a new modified wood material—Wood Polymer Composite. Maleic anhydride(Man) firstly penetrates into the porous structure of wood, followed by a reaction with wood cell walls. Then, Styrene(St) with some Man and a few amount of initiator, AIBN, permeate through the whole wood and react with the above modified wood. The structural characterization of wood polymer composite with SEM and FTIR indicates that Man reacts successfully with the hydroxyl group of wood cell wall by its anhydride group, and further reacts fully with styrene as a free radical copolymerization form by its double bond; and thus the polymer fills in wood cell lumina as a solid form, which combines the wood cell walls without any evident crack. The testing results of properties show that the mechanical properties of wood polymer composite increase by about 50%-250% over those of unmodified wood, and its durability improve 1.9-4.89 times than untreated wood.