Inspired from the natural porous structure of wood, a novel wood-polymer composite combining both advantages of wood with high strength-to-weight ratio as a natural renewable resource and polymer as a reinforcer was manufactured by synthesis of terpolymer of methyl methacrylate (MMA), Styrene (St) and Vinyl Acetate (VAc) inside wood. The three kinds of monomers with a few of 2,2'- azobisisobutyronitrile (AIBN) as an initiator, as well as some additives were first impregnated into wood porous structure under a pressure condition, and then initiated for terpolymerization through a catalyst-thermal treatment. The impregnating conditions containing pressure value and pressure time, and polymerizing crafts including heating temperature and heating time, as well as additive content were confirmed according to rate of monomer loading and rate of polymer loading inside wood. Results indicate that among these influencing factors, pressure and temperature were the significant influencing factors; and the rate of monomer loading and rate of polymer loading linearly positive correlated to them, respectively. SEM observation shows that the terpolymer fully filled in wood porous structure under the optimum manufacturing craft.