Abstract: Poplar wood fiberSiO2 composites were prepared via a solgel process for improving dimentional stability of fiberboards. The results showed that weight percent gain of wood fibers was reduced along with decreasing the concentration of the sol, but the gel particle was easy to permeate through the cell wall at low concentration. In order to keep the porous structure of wood fiber, the surplus sol on the surface and in the lumen was drawn out by vacuum. SiO2 gel could be found in wood cells by scanning electron microscopeenergy dispersive analysis. Si—O—Si bond was found from fourier transform infrared spectrophotometer. The dimentional stability of board was improved at a certain extent after modification by SiO2 gel.