Bio-based materials such as wood, bamboo, bio-straw material are vulnerable to degradation by microorganisms and susceptible to change in dimension under humidity, which greatly reduced their service life. In this study, a novel thought was inspired from the unique porous structure of bio-based material that durability of wood may be capable of being improved by generating polymer in situ the special structure. Maleic anhydride (Man) and Styrene (St) were used to penetrate into wood for further copolymerization. SEM observation shows that polymer filled in wood porous structure and tightly contacted wood matrix (i.e. biopolymers), indicating strong interaction between them. FTIR analysis indicates that polymer chemically grafted onto wood matrix by reaction of anhydride group and hydroxyl group. As the amount of hydroxyl groups greatly reduced for their reacting with polymer, the dimensional stability of wood immersing in water was improved; and as the reaction of wood with polymer, the biopolymers were wrapped by resultant polymer, preventing the sample from attack of microorganisms, thus decay resistance of treated wood against microorganisms was greatly improved. Both of them contributed to the improvement of wood durability.