A new composite, wood-polymer composite, was fabricated by formation of poly (methyl methacrylate) in wood cellular structure. Methyl methacrylate (MMA) monomer and a few of 2,2'- azobisisobutyronitrile (AIBN) as an initiator, as well as several drops of pyrimidine as catalyst were first impregnated into wood porous structure under a pressure condition, and then initiated for thermal polymerization through a catalyst-thermal treatment. The structure of Wood-PMMA Composite was characterized by SEM, FTIR, XRD, and its thermal stability was also examined. The results indicate that PMMA polymer generated in wood cellular structure as an amorphous form, and interacted with wood cell walls, resulting in chemical combination between them. The thermal stability of Wood-PMMA composite was higher than untreated wood under 450°C.