Abstract: 【Objective】Poplar fiber/Si-B composite was prepared, and its mechanical and antiseptic properties were studied.【Method】Using poplar fibers as the research materials, wood fiber/Si-Bcomposites were prepared via the sol-gel technology.【Results】According to scanning electron microscope-energydispersiveanalysis(SEM-EDXA),Si is present in wood fiber cell walls and the mass fraction of Si in the nanometer-scale pores of cell walls in the wood fiber can reach 3.08%. Fourier transform infrared spectrophotometry(FTIR)results showed a reduction in the number of hydroxyl groups(—OH)of the wood fiber, which is the main reason for the improvement of the dimensional stability of modified fiberboard which was produced with poplar fiber/Si-B composite.【Conclusion】The absorbing water thickness expansion rate of the modified fiberboard was lower than unmodified fiberboard, and the physical and mechanical performance meet the national standard. Moreover, the modified fiberboard also has good resistance to brown-rot fungus and, especially, for white-rot fungus.